Good day, and thank you for standing by. Welcome to the Silicon Motion fourth quarter 2021 earnings conference call. At this time, all participants are in a listen-only mode. After the speakers' presentation, there will be a question-and-answer session. To ask a question during the session, you will need to press Star one on your telephone. This conference call contains forward-looking statements within the meaning of Section 27A of the Securities Act of 1933 and Section 21E of the Securities Exchange Act of 1934 as amended. Such forward-looking statements include, without limitation, statements regarding trends in the semiconductor industry and our future results of operations, financial condition, and business prospects. Although such statements are based on our own information and information from other sources we believe to be reliable, you should not place undue reliance on them.
These statements involve risks and uncertainties, and actual market trends and our results may differ materially from those expressed or implied in these forward-looking statements for a variety of reasons. Potential risks and uncertainties include, but are not limited to, continued competitive pressure in the semiconductor industry and the effect of such pressure on prices, unpredictable changes in technology, and consumer demand for multimedia consumer electronics, such as any change in our relationship with our major customers and changes in political, economic, legal, and social conditions in Taiwan. For additional discussion of these risks and uncertainties and other factors, please see the documents we file from time to time with the Securities and Exchange Commission. We assume no obligation to update any forward-looking statements which apply only as of the date of this conference call. Well, please be advised that today's conference is being recorded. And if you require further assistance please press Star zero.
Now I'd like to hand the conference over to your first speaker today, Mr. Chris Chaney, Director of Investor Relations and Strategy. Please go ahead, sir.
Thank you, Amber. Good morning, everyone, and welcome to Silicon Motion's fourth quarter 2021 financial results conference call and webcast. As Amber mentioned, my name's Chris Chaney. I'm the Director of Investor Relations here at Silicon Motion. Joining me today on this call are Wallace Kou, the President and CEO, and Riyadh Lai, our Chief Financial Officer. Following my comments, Wallace will provide a review of our key business developments, and then Riyadh will discuss our fourth quarter and full-year results and our outlook for the upcoming year. We'll then conclude with a question-and-answer period. Before we get started, I'd like to remind you of our Safe Harbor policy, which Amber read at the start of this call. For a comprehensive overview of the risks involved in investing in our securities, please refer to our filings with the U.S. Securities and Exchange Commission.
For more details on our financial results, please refer to our press release, which was filed on Form 6-K after the close of the market yesterday. This webcast will be available for replay in the investor relations section of our website for a limited time. To enhance investors' understanding of our ongoing economic performance, we will discuss non-GAAP information during this call. We use non-GAAP financial measures internally to evaluate and manage our operations. We have therefore chosen to provide this information to enable you to perform comparisons of our operating results in a manner similar to how we analyze our own operating results. The reconciliation of GAAP to non-GAAP financial data can be found in our earnings release issued yesterday. We ask that you review it in conjunction with this call. Now with that, I'd like to turn the call over to Wallace Kou.
Thank you, Chris. Hello, everyone, and welcome to our earnings call. Silicon Motion just wrapped up a stellar year, and we believe we are now gearing up for another great year. Our fourth quarter sales were up 84% year-over-year, and full-year sales grew 71%. Our fourth quarter earnings per ADS were up over 120% year-over-year, and full-year earnings grew over 90%. Our 2021 business activities were extremely strong, and we are seeing much of this momentum continuing into 2022. Last year, demand for our SSD controllers using OEM program for PC and other client devices, as well as our eMMC and UFS embedded storage controllers used in smartphones, automotive, IoT, and smart devices, was tremendous, and demand from OEM continued to be very strong. Last year, we delivered corporate record sales.
Despite our very strong sales, we could not meet the full demand of customers who were building SSD and other storage devices for OEM in many categories of applications. We are not able to meet their full demand because our business was supply-constrained, constrained by a limited availability of foundry wafer supply necessary for fabricating our ICs. Today, supply continues to be very tight, and we don't expect this situation to change this year. As previously discussed, our order book was significantly backlogged last year, and today this backlog remains significant. Early last year, we originally communicated a 20%-30% sales growth guidance for full- year 2021. This revenue guidance was based on both meaningful incremental foundry wafer supply allocated to us, as well as existing product mix and pricing arrangements.
From that starting point, our operations team was able to meaningfully upsize sales growth to 71% for full- year 2021 by optimizing our product mix, customer allocation and pricing. Now turning to this year. For full- year 2022, we have again received meaningful incremental wafer supply from our primary foundry partner. Based on this incremental wafer supply, we will be able to grow full- year sales 20%-30%. We believe, however, that there are opportunity for us to grow even faster than this baseline range, and our operations team has already begun implementing strategic initiatives with the aim of delivering upside to baseline. Upside opportunity include better product optimization, additional wafer supply and pricing. I look forward to sharing with you more on this in the following quarters as we can successfully execute.
Sales of both our SSD controller and eMMC plus UFS controller were extremely strong. Now let me talk about each one of these two key product lines. Full-year sales of SSD controller grew 75%-80%, significantly faster than the market. In 2021, we likely gained close to 10 percentage points of market share with full-year client SSD controller market share today that is roughly in the 35%-40% range. Our SSD controller growth were driven by extensive adoption of SSD by PC OEM using our controllers. Sales to almost every one of our key customers involving OEM program, whether NAND flash makers or module makers, grew strongly and we expect the significance of our sales to OEM to continue to increase.
The portion of our SSD controller using OEM program grew to account for well over half of all our SSD controller sales in the second half of 2021, significantly higher than 1/3 the year before. The rest are controllers for channel market. We anticipate the significance of OEM program to grow further and account for close to 2/3 of our overall SSD controller sales this year. Last year, we saw the continued ramp-up in sales of our PCIe Gen 3 SSD controller, which have been widely adopted by PC OEMs. In the second half of this year, we launched the first generation of our PCIe Gen 4 series of SSD controller also to OEM.
The rollout of Gen 4 with OEM lagged our initial launch for our Gen 4 into the channel market by well over a year because of extensive verification and testing by both our direct customers and the PC OEMs. We are now initiating the launch of our second generation PCIe Gen 4 controller and expect Gen 4 to account for a majority of SSD controller sales this year, which coincide with the accelerating broad-based adoption of PCIe Gen 4 SSD by PC OEMs. We believe that we will continue to gain market share this year. Based on the design win and sale projection, we expect our controller to be in half of all of PCIe Gen 4 socket at PC OEM by the end of this year or early next year when our Gen 4 programs are scaled.
Additionally, our NAND flash customers continue to work with game console OEMs for the adoption of our SSD controller in their next major device upgrade cycle next year. It is likely that PCIe Gen 4 will last a few years since Intel and AMD both continue to bring new upgrade variant of CPU with PCIe Gen 4 to the market. Similarly, we are preparing for the launch of our third generation PCIe Gen 4 controller next year before transitioning to PCIe Gen 5 in the following year. Before moving to our eMMC plus UFS controller, let me provide an update on our enterprise SSD controllers. As many of you know, we have been investing actively for several years in enterprise class SSD controller R&D. We have been investing in our understanding of the large, complex and fragmented market, and the technology necessary for bringing differentiated and compelling solution to customers.
The design cycle in the enterprise market are also much longer than the client and mobile markets. Our current product, before the upcoming launch of our flagship enterprise class PCIe Gen 5 controller, are finally completing final customer testing and qualification and moving to production sale this year. We are currently rolling out our enterprise class SATA SSD controller for the large volume, long tail, well-established enterprise market. Separately, our turnkey PCIe Gen4 SSD controller with robust firmware that is performance tuned for certain enterprise data center applications. Additionally, we are on track to begin sampling our flagship SM8366 PCIe Gen5 SSD controller in the second half of this year.
We believe our Gen5 is uniquely positioned with both very competitive operational performance and robust architecture, and is also compellingly differentiated with features designed, desired by hyperscale and enterprise customers, such as highly customizable firmware, performance shaping capability, and optimized data placement technologies. We believe we are well-positioned to repeat the success we had achieving client SSD controller in the enterprise SSD controller area as well. Now let me turn to our eMMC plus UFS controllers. Last year, sales of both eMMC controller and UFS controller roughly doubled, with growth coming primarily from market share gains. Sales of the UFS controller grew strongly as our U.S. NAND flash customer continued to expand aggressively to build its market position with smartphone OEMs. Our UFS controller sales also benefited from growing sales to other customers.
We are seeing renewed growth in sales of our classic eMMC controller from the proliferation of new applications, such as automotive with ADAS, telematics, and entertainment system that use eMMC, but also from the opportunity created as many of the NAND flash makers began to exit from this older low capacity storage technology. We have benefited from supplying controllers to module makers stepping into the market. Additionally, a few NAND flash makers who are facing foundry wafer supply issues are also outsourcing eMMC controllers from us. This is attractive market for us because we are the only meaningful merchant supplier of eMMC controllers, and the eMMC market is relatively big, with annual market sales volume of approximately 1.5 billion units. Now I will turn the call over to Riyadh to discuss financial results and our outlook.
Thank you, Wallace, and good morning, everyone. I will discuss additional details of our fourth quarter and full- year results and then provide our guidance. Please note that my comments today will focus primarily on our non-GAAP results, unless otherwise specifically noted. A reconciliation of our GAAP to non-GAAP data is included with the earnings release issued yesterday. In the fourth quarter, sales were $264 million, growing 4% sequentially. Earnings per ADS were $1.90, which was 12% higher sequentially. For the full- year, sales were $922 million, up 71% versus the prior year. Earnings per ADS were $6.21, up 92% from the prior year. Now I'll review the performance of our three key products.
SSD controller sales grew 15%-20% sequentially in the fourth quarter, reversing third quarter's approximately flat sequentially as we allocated production back to SSD controllers. Full- year SSD controller sales grew 75%-80%, far exceeding the market's growth rate as we gained significant market share. Full- year SSD controller sales accounted for approximately 55%-60% of our total sales. eMMC plus UFS controller sales declined 5%-10% sequentially, reversing third quarter's sharp sequential growth as we coordinated production with our SSD controllers. Full- year eMMC plus UFS sales grew 105% and between 105% and 110%, far exceeding market growth as we gained significant market shares. Full- year eMMC plus UFS sales accounted for approximately 30%-35% of our total sales.
SSD solution sales in the fourth quarter grew 5%-10% sequentially. For the full- year, SSD solution sales declined 5%-10% and accounted for approximately 5%-10% of our total sales. Gross margin in the fourth quarter were 49.9%, consistent with the prior quarter. For the full- year, gross margin was 50.4%, 1.3% points higher than the prior year's 49.2%, as we focus on optimizing our product mix and customer allocation and repricing our products to account for higher costs. Operating expenses in the fourth quarter were $50.3 million, $2.7 million lower than the prior quarter, primarily due to sequentially lower tape-out expenses.
Operating expenses for the full- year were $195.5 million, up $47.8 million from the prior year, primarily due to higher bonuses. Tape-out expenses were also higher, as were salaries, as we expanded our headcount, mainly R&D engineers, and implemented routine wage increases. Operating expenses as a percentage of revenue for the full- year were 21% for the full year, down from 27% in the prior year. Operating margin increased from 29.4% in the prior quarter to 30.9% in the fourth quarter, the highest in our recent corporate history. Full- year operating margin was 29.2%, up significantly from 21.8% the prior year, as we benefited from significant operating leverage and a slightly higher gross margin.
Our effective tax rate in the fourth quarter was temporarily lower at 70%. For the full- year, our effective tax rate was 19%, close to our 20% mobile tax rate. Stock-based compensation and operating expenses, which we exclude from our non-GAAP results, was $9 million in the fourth quarter at the low end of our $9 million-$10 million guidance. We had $405.5 million of cash equivalents, restricted cash and short-term investments at the end of the fourth quarter, comparable to the $419.4 million at the end of the third quarter. Our inventory levels remain extremely lean as foundry capacity continues to be very tight and demand remains robust.
In the fourth quarter, we had 110 days of inventory, two days less than the prior quarter and 18 days less than a year ago. Our controller inventory is even leaner at 30% of our inventory at the end of December, as 30% of our inventory at the end of December are for SSD solution, and SSD solutions are less than 10% of total sales. We currently only have a couple weeks of controller finished products in inventory to sell. We paid $17.4 million in dividend to shareholders, the first quarterly installment of our $2 per ADS annual dividend that was declared last October. We are aggressively repurchasing our shares. In the fourth quarter, we spent $50 million repurchasing our shares.
We expect to repurchase another $50 million in January and the remaining $100 million by June of this year. In terms of other major uses of cash, we also had $11.2 million in CapEx. Now let me turn to our guidance and forward-looking business trends, starting with our revenue guidance. For the full- year, we are expecting revenue to grow 20%-30%. This is revenue growth forecast. This revenue growth forecast is based entirely on incremental foundry wafer supply. Also note we received more incremental wafer supply allocation in the second half of this year versus in the first half, and the timing of this is an important factor for driving our sequential growth through the rest of this year. As Wallace had mentioned, this is our baseline target range and we are undertaking initiatives to deliver upside to this.
The upsizing of our revenue guidance is dependent on the successful execution of certain operating initiatives. First quarter revenue is expected to decline 10%-15% sequentially. This sequential decline is primarily the result of two factors, timing of our Wafer Supply and China channel market inventory cleanup. We received meaningful incremental wafer supply this year, but the timing of the availability of supply is not linear and will impact us in Q1. Wafer supply for certain key nodes in Q1 will be less than in Q4, which means we will have fewer high demand parts to sell. As I had said a few minutes ago, we are currently operating at very low inventory levels with just a couple weeks of finished goods of controllers.
Furthermore, for parts with better supply availability, module makers operating in China's channel market have reduced procurement to clean up their inventory before the long Chinese New Year holidays. We believe this action is temporary as module makers are trying to reduce their inventory holding risk before the long holiday. Positively, we are seeing recovery of the channel market, both in terms of sentiment as well as business activity, as module makers are now more willing to build products than a quarter ago. Our module maker customers targeting the channel market are now actively discussing with us about controllers to support their upcoming NAND flash procurement. Fortunately, our new OEM programs are not affected as these programs are the new programs only beginning and will pick up and accelerate over the next few quarters.
We are already 1/3 of the way through the first quarter and see good improvement in sales next quarter. We expect sequential growth through the rest of the year, with growth coming from the scheduled ramp of new OEM programs, which will be supported by the timing of incremental wafer supply already allocated to us. Let me now turn to our gross margin guidance. For the full- year, we are expecting gross margin in the 49%-51% range. We believe we can continue to manage our products around our 50% target gross margin. First quarter gross margin should be in the 49.5%-51.5% range. Turning to our operating margin guidance. For the full- year, we're expecting operating margin in the 29%-31% range. We are delighted that we are now delivering towards our 30% target operating margin.
First quarter operating margin should be in the range of 27.5%-29.5%, lower than in the fourth quarter because of higher tape-out expenses. For our other key modeling assumptions, for the full- year, we expect stock-based compensation to be in the $22 million-$24 million range. First quarter stock-based compensation should be in the $5 million-$6 million range. We expect our effective tax rate for 2022 to be approximately 20%. For the full- year, we expect approximately $45 million of CapEx, of which $18 million will be for routine CapEx and $27 million for our Hsinchu and Taipei office building construction. First quarter CapEx should be approximately $14 million, of which $6 million will be for routine CapEx and $8 million for our office building. This concludes our prepared remarks.
We will now open the call to your questions.
Thank you. We will now begin the question- and- answer session. As a reminder, if you wish to ask a question, please press Star one on your telephone and wait for your name to be announced. If you wish to withdraw your request, please press the Pound or Hash key. Our first question comes from the line of Craig Ellis from B. Riley Securities. Please go ahead.
Yeah, thanks for taking the question, and team, congratulations on the very strong performance in calendar 2021. Wallace, I wanted to start off with maybe a bigger picture, longer-term question. As I look back at 2020 to 2021, you had strong share gain and growth in really all of your markets, and it looks like that demand strength and that order strength is persistent in 2022, and then it sounds like SSD Solutions has a new product ramp that could augment your product mix and growth in 2023.
The question is this: as you look at the business and the share gain potential across SSD controllers, eMMC and UFS, put in context when you last saw this type of growth for the company and your confidence today in the ability to execute against that growth the way that you did last year?
Great. I think you asked a very good question. If you look at the big picture, if we can secure enough wafer supply, we believe the growth momentum will continue for next three to five years. We do see we have a lot of headroom to grow, particularly in client SSD, eMMC and UFS controller. For client SSD, we believe by 2023, we should have at least one major client SSD project for all NAND makers, and we have confidence to achieve that. We believe our eMMC controller will continue to grow with benefiting from the NAND maker, they are all sourcing. Some of NAND maker also into us, and we grow with the incremental of the new application for IoT device and smart devices, including low-end smartphone. UFS, we also gain market share with additional customer.
We believe the momentum will continue to grow when UFS become more popular in the smartphone market. I think if we can keep execution for all our major project program, and we can recruit talented R&D in time, and we get sufficient wafer, the growth momentum will continue for next three to five years.
That's helpful. For my follow-up question, I'll switch it over to Riyadh. Riyadh, one of the things that characterized last year was the four different initiatives that the company was executing on regarding cost management, fulfillment, et cetera, to execute gross margin, which played out very well through the year. As we look at the first quarter's guidance and the full- year guidance, it does imply some gross margin decrease through the year. The question is this: what is the momentum that you have operationally on things that benefited gross margin last year, and what are some of the potential pressures on gross margin as you look through the year, and what levers do you have to offset those?
Craig, we are continuing to look at our business and look for ways to improve that, similar to what we were doing with our business a year ago. There are certain initiatives relating to product mix, pricing, wafers, and other costs that we are looking into, which we plan to execute. While the growth baseline remains the same. The baseline is what we have communicated. There are potentially opportunities where we can deliver better results in terms of top line and also better results in gross margin relating to, you know, the upselling of a richer mix of products that we did last year, optimization of our product mix allocation to customers, which again, we also did quite nicely last year.
Better pricing discipline, which we will continue to press ahead this year. Furthermore, on the cost of sales side, we also continue to look very carefully about our manufacturing processes, where there are opportunities to tune our yields to reflect a better costing. We'll certainly be pressing on that. This is in terms of both the fabrication of products as well as the back end and other elements of our manufacturing processes. There are opportunities that we're continuing to look into in order to improve our profitability.
That's helpful. If I could just sneak in one more before hopping back in the queue. Congratulations on the strong start on the share buyback program, and I appreciate all the visibility into how you execute the program as you go through the first half of the year. At the risk of putting the cart a little bit before the horse, can you just talk about the executive teams and the board's view on what could happen after the first half of the year? Is share buyback something the company would entertain in the back half, given the level of operating cash flow and the degree to which free cash flow is well above CapEx needs for the new building that's underway and the dividend program that's been nicely enhanced of late? Thank you.
Craig, that's a great question. We have a business that's highly cash generative. If you look at our fourth quarter, our cash balance at the start of quarter and end of quarter is little change despite $50 million of share repurchase, over $17 million of dividends paid to shareholders, plus CapEx and other elements. We clearly have the cash flow to continue to do a lot of attractive initiatives to boost our shareholder value. Let us first complete our current shareholder program, share buyback program, and we can certainly look into other initiatives or continuation of this type of initiatives later this year.
Fair enough. Thanks, guys.
Thank you. Our next question comes from the line of Rajvindra Gill from Needham & Company. Please ask your question.
Yes, thank you, and I echo my congratulations on the stellar results in calendar 2021. Wallace and Riyadh, when you look to calendar 2022, and you were very clear about saying that the 20%-30% outlook is a baseline target, and it will be based on, and the upside could be driven by certain variables, incremental wafer supply, product optimization, et cetera. I'm wondering how you're thinking about the timing of that. You know, you mentioned in Q1 that the sequential decline in revenue is driven because of the timing of capacity not happening. So my question is, how confident are you that you will get the incremental capacity at the timing that you need?
What reassurances is TSMC providing you that gives you that confidence, not only to provide a 20%-30% outlook, but essentially say there could be upside to that, if we get more supply throughout the year?
I think you raised a very good question as to how confident we are regarding from a baseline guidance to move to the upside. I think the primary rely on the additional wafer supply from TSMC, as well as how we can pull in the wafer allocation to us from second half to first half. I think, as we mentioned, we are in severe shortage in certain technology nodes, including 55 nm and all advanced technology node, 60-nanometer and 12 nm. However, I think we are comfortable in 28 nm wafer supply. We are just battling the 40 nm. If we cannot get any additional wafer supply from TSMC, and this all depend how we can fully utilize 28 nm with the better product mix and with the pricing with the customer.
So far, we believe we could benefit from some potential wafer supply with our primary foundry supplier, and we are discussing almost every week, and we see there's a positive momentum. In addition, our primary customer is also helping us to get a wafer supply from TSMC. I think that momentum and direction will be very helpful and positive.
Okay, great. That's helpful to understand. Staying on Q1, the channel inventory cleanup in China, which is leading to a decline in Q1 2022, you mentioned that, you know, these module makers are starting to build more inventory, or indications that they'll do that post the holiday season to support the NAND flash procurement. I wonder if you kind of elaborate a little bit further on how the module makers are thinking about their products this year. The OEM programs are very strong and that's and it's great to hear that that's gonna represent, you know, two-thirds of the controller sales. Trying to get a better understanding of the module makers as we progress throughout this year.
Okay. Let me try to clarify regarding the situation that Q1 we face. I think module makers, they are opportunity takers. Because the Chinese New Year is coming, so most of them, our customer try to reduce inventory to reduce the risk because the NAND pricing is still a lot of uncertainty. Although the Xi'an fab lockdown impacts Samsung's production output. I think all the module maker, they are expecting NAND price decline continually. They are hesitate to really capture very large volume of NAND, so they don't need a more controlling inventory. However, lately, we do see all the module customer from China, they are actually discuss about the new procurement program, which we see from the backlog from our Q2 and Q3.
These are really very very active across all our major customers in China and in Taiwan. We see this as very good momentum, and we check with the channel. It looks like the channel inventory now is also very low in China, and the activity is very active. This is a very positive move, and we see the backlog moving up very strong, even with the mature technologies, particularly in the legacy node. This is helpful for it to increase our confidence the China market will recover strongly from late Q1 to Q2.
Very good. Thank you.
Thank you. Our next question comes from the line of Karl Ackerman from Cowen & Company. Please state your question.
Yes. Thank you, gentlemen. Two questions, if I may. Riyadh, I was hoping you could help me bridge the outlook for March and the full- year guide by discussing whether customers have signed or cemented volume orders for these PCIe 4 controllers that gives you the confidence in a big snapback in revenue beyond the March quarter. As you address that question, is there a way to quantify the impact in March from a moderation or push out of client SSDs, given these supply chain disruptions impacting PC assembly?
Karl, for your question relating to PCIe Gen 4 purchase orders from our customer, I'll defer that question to Wallace, who provide more better insight into this. I think our PCIe Gen 4 program is that we have multiple PCIe Gen 4 program with PC OEM from five different NAND maker and four different module makers simultaneously. The ramp-up is based on their own internal program process. There's a very intensive qualification and testing, also NAND procurement. We do not see the schedule for some of OEM, they are on track. For some, they are a little push out due to the delay from both our internal resource issue and the NAND maker their own decision. I cannot comment the detail.
As the backlog is very, very strong, we do not see any impact from the backlog. Frankly speaking, all the major new PCIe Gen 4 are 12 nm technology node, and we just don't have enough wafer to support the demand to fill. If we have a sufficient, I think we will revise guidance immediately. In addition, our UFS 3.1 controller uses a TSMC 60 nm. We also have a severe shortage. Even TSMC increases capacity compared with 2021, but still not enough to meet our customer demand in 2022. We'll continue to work with our customer, with TSMC together to gain additional wafer supply. That's our baseline guidance, 20%-30% growth based on current wafer allocation to us.
That's very helpful. I appreciate that. For my follow-up, I did wanna touch on your PCIe 5 enterprise controllers. I know you've indicated that you are moving into production this year, but could you also discuss the design engagements you have on enterprise controllers broadly, both for PCIe 5 as well as PCIe 4 products that you have available today? I guess as you address that question, is the growth of enterprise controllers a big driver, a small driver? What sort of driver to your full- year outlook? Thank you very much.
I think probably I did not speak clearly. We are going to sampling our PCIe Gen 5 enterprise controller in second half this year. It will be in production in second half of next year, 2023. The PCIe Gen 5 flagship enterprise controller, we believe that will be uniquely positioned for very high-end, high performance driver for enterprise customers, especially the hyperscale customer. It's designed for high-end enterprise server as well as data center providers. We believe this product will win quite a lot of the major design. We are in frequent discussions with the potential major customer. Currently, this year, we are ramping our SATA enterprise controller with a high volume and our PCIe Gen 4 controller, which is not a leading controller, but we also win some incremental customer, and we're going to ramp up in second half this year.
Thank you.
Thank you. Our next question comes from the line of Suji Desilva from ROTH Capital. Please go ahead.
Hi, Wallace, Riyadh. Congrats on the strong year there. Looking ahead to calendar 2022, it sounds like you're kind of setting it up the same way as the beginning of calendar 2021, the guide, and then the potential for upside with wafer allocation. How does the beginning of 2022 feel different perhaps from the setup in 2021, where you did upside the numbers just in terms of supply chain and capacity? Just be curious to know the differences.
I think that as we mentioned from the early 2021, we start to work with TSMC for 2022 wafer supply. We understand 2022 wafer supply in particular technology node, they are more severe than 2021. I think TSMC is recognizing the importance of our position as a technology provider for major customer in certain market sector. We do get an incremental wafer, especially in 16 nm and 12 nm technology nodes. This year, the different, major difference is we have much broader OEM-based customers and much stronger market-leading position from both client SSD, eMMC and UFS controller because we have a multiple UFS controller will go production this year. Now, we do face even the wafer allocation we got, we can only grow as our guidance 20%-30%.
However, this opportunity, which is we set a model like last year, our major customer will also helping us to asking additional wafer supply from TSMC. If there's any customer cancellation or any opportunity, I think we might be able to get incremental wafer in second half this year. I think we just keep a focus on what we are doing and try to maximize the wafer we're using for product mix. As I mentioned, 28 nm, we are a little comfortable. We could do a better wafer allocation in 20 nm to gain incremental sale revenue and even without the additional allocation in advanced technology nodes.
Great. Thank you. It's helpful to have that contrast versus 12 months ago. Then, I think your next growth opportunity is really this high-end enterprise SSD controller or just enterprise SSD controllers in general. Can you talk about how, if any, ways the competitive landscape there is different from the SSD controller business where you've been so strong and gained 10% share this year? Wanna understand the competitive dynamics, how many subtle differences that we should note.
Yeah. As you know well, we spend investment for enterprise SSD controller for almost four years by now. We do gain tremendous lessons. We also gain technology and then experience from previous two generation. Now, I think that we from the architecture-wise, our second generation enterprise SSD controller stays behind the leading the leader in the market. However, the PCIe Gen 5 enterprise controller is our third generation. We really learn enough lesson how to really create a really enterprise type controller architecture to meet the customer demand and expectation, particularly in latency and also the rewrite combination performance and all the key features and custom asks, we all deliver into the silicon.
In addition, we also spend great effort to do the modeling for the computer architecture NAND, and also do the performance tuning algorithm with the dedicated firmware teams. Now, we believe our firmware technology in enterprise SSD will be similar or same level with the leader in the market today. That's why we have a pretty good confidence when we launch enterprise, our PCIe Gen 5 controller, we should have a pretty decent position in the market.
Sounds like a good setup. Best of luck with that. Thanks, guys.
Thank you. Your next question comes from the line of Anthony Stoss from Craig-Hallum. Please go ahead.
I also wanted to follow- up a little bit on the enterprise controller side, Wallace. You know, ahead of shipping samples in the second half of this calendar year, you are exuding a ton of confidence entering that market just like you did the PC OEM side. Is it just based on conversations since you haven't sampled solutions yet? Then also maybe two quickies for Riyadh, just updating kind of the order book size. Then also maybe for you, Wallace, as well, the Q1 limitation that you're getting now from TSMC, when did you learn of this change? Is it something that you've known for a while or is it more recent? Thanks.
I think you have probably two or three different questions. Let's just try the enterprise side. Enterprise, I think, we start to, as we said, have a volume shipment for SATA enterprise controller this year. Our PCIe Gen 4 controller is incremental sales, although we understand that's not a leading controller today, but we are able to secure few customers to sell the PCIe Gen 4 as a vehicle to introduce our PCIe Gen 5 enterprise controller, which will be sampling in second half this year and production in second half of next year.
Regarding the wafer allocation and discussion with the primary foundry maker, I cannot discuss detail, but I think the TSMC, they definitely were based on the market need and also to avoid the short side and long side unbalanced supply, right? Automotive is probably most critical sector. There are several other market sectors to avoid the breakdown. They were based on the market survey and the feedback based on end customer's need and to do the allocation. I think we do have a very strong design win, especially PCIe Gen4. We believe our program will occupy probably 50% of all PCIe Gen4 from PC OEM. That's significant. TSMC have to consider because if there are shortage, it may cause a certain problem for the major supply chain for the notebook shipment.
In addition, I think same thing for smartphone, all the UFS for major smartphone customer. This is very important for the foundry maker. I believe there are some discussion going on. We cannot comment the detail. Hopefully, we can get an incremental wafer supply on second half of this year.
Tony, I'll now try to address your other question, your third question relating to the sizing of our order book. Our order book has continued to grow. Wallace had briefly touched upon that in his comments a little while ago. Our order books have continued to grow. One way to look at this is to look at our order book versus our actual sales. This ratio last year versus today has remained just as broad. The ratio remains similar to what it was a year ago. The strength of our order book has remained quite strong and quite sizable.
Bear in mind, you know, when we talk about our order book, we're also talking about our adjusted order book. We're discounting the orders from module makers that are more opportunistic with more limited visibility and focusing more on the higher quality stuff. Even with the higher quality visibility, it still remains very significant to what we're able to deliver this year, comparable to what it was a year ago.
Thanks, guys. Great execution. Thank you.
Thank you. Our next question comes from Donnie Teng from Nomura. Please go ahead.
Hi, good evening, CEO and CFO. Congrats on very strong 2021 results. Two questions. First one is, I'm interested in the game console business opportunity for this year, if I heard correctly. Wallace, could you kindly elaborate more on this opportunity? Is this for OEM or aftermarket? And also, are you replacing the existing suppliers or it's like you are the additional suppliers to this game console opportunity? Thank you.
As I mentioned, this year is not the new generation, it will be 2023 launch. This year just refresh. We are now in the refresh cycle. Game console customer player want to maintain the same solution continually. I think we will go through two NAND maker to win the game console socket next year. I cannot comment whether we replace existing player or additional controller maker.
Got it. Is it a OEM business or aftermarket business?
OEM business.
Okay. Thank you. My second question is regarding to the UFS. I think so far we have a very powerful 2754 UFS 3.1 controller, right? I'm just curious, do we have any new generation or new upgrade for this IC maybe beyond second half this year with our leading U.S. customer? Also, considering UFS has been also replacing eMMC controller quickly this year, right? Just curious regarding to your full year sales growth guidance, 20%-30%. How would you think about the growth momentum in between SSD controllers and the UFS controllers? Thank you.
Okay. Let me just, probably is not appropriate to give you the whole product roadmap, but I should tell you, our UFS are going to have two more new product coming for second half this year. One is also UFS 3.1, the other is UFS 4.0. UFS 3.1 is really to support the new generation of NAND. Because the new generation of NAND, the DDR will go to 2400 or DDR over 3000. So you don't need that many channels for NAND. So in order to be more cost effective and also high performance, especially in random and read, and we have a new architecture design for this new controller, and cost will be cheaper than SM2754. Performance could be even better. Because that.
More suitable for the 176-layer or beyond, especially above 200-layer TLC, as well as the QLC NAND. For UFS 4.0, it's really designed for very high end, and we want to be ahead of even some NAND makers, so we can provide the value add to the NAND maker customers. Regarding the UFS sale revenue, I cannot comment for that because I just cannot. I can just tell you the demand much more than I can support. Even our customer try very hard to consign additional wafer, still not enough to support the demand.
Donny, let me also add, this year our growth is not only quite strong, but it's also very balanced. We have very strong growth from our client SSD controllers. We also have very strong growth from our eMMC plus UFS controllers. When you look into that one layer below, growth is not coming just because of one of the two legs of UFS plus eMMC, but rather growth is coming from both legs of eMMC. Strong growth from our eMMC controllers, as well as strong growth from our UFS controllers. We believe that this will carry over into next year.
Got it. Very helpful. Thank you, Wallace and Riyadh. Congrats.
Great. Thank you. Th ere are no further questions. I'll now turn the call back to CEO for closing remarks.
Thank you everyone for joining us today and for your continuing interest in Silicon Motion. We'll be attending several virtual investor conferences over the next few months. The schedule of these events will be posted on the investor relations section of our corporate website. Thank you everyone for joining tonight. Goodbye for now.
Thank you. That does conclude our conference for today. Thank you for participating.