As many of you know Bitcoin prices have surged recently up to $40,000 USD per bitcoin as of February 2021. We are in the middle of a bit rush! People are noticing Bitcoin’s surge and wondering how they can profit from it. In this article we will explore how custom silicon is a vital part of a winning bitcoin mining strategy.

Some people wonder what it would take to make their own Bitcoin mining custom silicon in order to beat everyone else. My quick survey of the field indicates Bitmain Antminer S19 Pro is the state of the art bitcoin mining equipment as of February 2021. Just as many others such as Amazon, Apple, Facebook, Tesla, Google and more have realized that there is a clear competitive advantage to their businesses from custom silicon; Bitmain too decided to make their own custom silicon.

Using the latest silicon process node increases the power efficiency and the processing power of the bitcoin miner system. This is why bitcoin miner systems manufacturers continue to update their custom silicon mining chips.

Some things to consider to plan your next custom silicon mining chip:

• Selecting a chip supplier to design your custom silicon (i.e. ASIC).

Finding a good chip supplier to design your ASIC is an art in and of itself. You want a reputable company with an excellent design team, but they also want a reputable system company as a customer.  So if this is your first project making a bitcoin miner you will need to convince the chip supplier (among others) that you’re a serious customer. There are many chip design houses in the world, but many of them are not probably who you’d want to hire if you want to reduce your technical and schedule risks. A way to mitigate your risk of selecting the wrong supplier and also to present your RFQ professionally is by hiring a silicon manager to assist you in those interactions. As part of CustomSilicon.com’s process we work through the Concept and Requirements phase with the chip supplier candidates, and end up selecting one candidate after the Si proposal review. I’d go for 4 chip supplier candidates at Concept, reduce that to 2 suppliers at Concept phase sign-off and then at Requirements phase sign off downselect to 1 chip supplier.

You want to buy RTL IP that is ready for use or hire a chip supplier that has it from past projects. There are some companies out there with previous experience designing custom ASICs for bitcoin mining. But you always need to thoroughly vet them before moving forward writing checks for NRE and masks.

• Project cost.

There are some costs that are more predictable than others. A disclaimer: all prices below are my gut feeling/what I read/hear from others, from my experience, etc… But as you should know many prices are negotiable and these are influenced by your relationships, total volumes, cost of opportunity of the supplier, negotiating skills, etc…Here are some:

• 1. Masks: To make a chip at the foundry you need to buy masks. ASICs today for bitcoin mining are in the 7 nm node already. So if you want to leapfrog the competition you need to shoot for 5 nm or 3 nm. 3nm is the highest risk since this process node is in development.  In my opinion masks for a 5 nm or 3 nm process will be in the 10 to 14 million USD range, let’s call it 12 million USD for easy math. A project like this will probably take two full mask sets on a good case scenario. Selecting a good supplier, performing detailed reviews, using state of the art EDA tools, getting direct foundry support, and hiring a silicon manager are all good ways to mitigate the risk of needing to tape out more than two times.
  2. NRE: This is the cost to pay for the chip design house. This is really subjective and speculative before having gone through Concept and Requirements phases since it will depend on how closely the RTL they have matches the requirements the system company wants and what trade offs you negotiate. It also depends on foundry rule deck accuracy, and simply put what other things that chip design house could work on since that is an opportunity cost for them. In my opinion this will land in the 2 to 5 million USD range. But this can really vary depending on negotiations and everything mentioned here.
     • Firmware: Here it’s important to decide who will write the firmware for the chip. This can actually be a significant cost comparable to chip designer time cost and sometimes exceeding it.
     • Assembly and test: It’s possible that the chip design house is not going to provide a full solution. In that case you need to go work with an outsourced assembly and test (OSAT) house.
     • Ideally you don’t need to go through one of the value chain aggregators (VCAs) to work with the wafer foundry, but that could happen. I think working direct with the foundry will help your project go faster and reduce errors, but the foundries don’t want to work directly with startups (i.e. companies with small volume). So the point made further below in this article about buying foundry wafers is key to gain direct foundry access.
  3. Summary of fixed costs: 24 Million USD (assuming two full mask sets) + 2 to 5 Million USD (NRE) = 26 to 29 Million USD

• Project schedule.

  1. My gut feeling is that getting from Concept phase start to Requirements phase sign off is probably a 3 months endeavor.
  2. Time from spec freeze to tape out is probably in the 6 months range. This could be longer or shorter depending on how close the starting RTL is to what the system company wants from its miner.  It’s important to highlight that specification freeze requires the system company to develop concise, precise and complete requirements documentation during the Concept and Requirements phases. This is important so that the chip supplier can provide a draft specification quickly after Requirements phase sign-off and we can close on the specification of the chip with Specification phase sign-off. Constant spec changes during development are a project schedule and cost nightmare that can be avoided with disciplined process and early attention to detail.
  3. Time from tape out to tested samples is probably 5 months.
  4. Time to first samples: So time to first ASIC samples is equal to 1+2+3. Which is 14 months for your late Proto or first EVT build.
  5. You will likely need to spin the silicon one more time to get to final shippable silicon. This likely means 2 months of Validation time , 2 months to get ready for the tape out and 5 months of fabrication time. You will have to be thorough at chip and system level validation to find all bugs. Then later check that the ECOs are properly root caused and verified before tape out.  So your final silicon samples (i.e. not production quantities) come in at 23 months for your DVT build.
  6. Mass production risk ramp is another area where you will need to make a judgement call. This will be about how much money you want to risk without knowing that the final silicon is good yet (i.e. you haven’t completed your DVT build).  You can decide to pull in the bitcoin miner system’s mass production ramp date by risk releasing wafers before building DVT phase. To do that you need to go through all your validation status and make a risk assessment in preparation for Mass production phase sign-off leading to your PVT (i.e. final) build. It takes about 5 months to get mass production parts in volume. So if you waited to build systems with final silicon samples until 23 months and then signed off on ramping the wafers at DVT build exit sign off, it will take another 5 months (plus some assembly packaging and test time) to get those mass production chips in quantity to your factory. Risk released wafers could end up being scrapped if you find bugs at DVT that are unacceptable with your final silicon. So this needs to be done with care as it can cost you millions of dollars in scrapped wafer material. Sometimes bugs can be fixed with one time programmable memory (OTP) at final test which would save you from having to scrap the wafers. So you will want to plan to lock OTP settings sometime before you would need to run chips through final test for your mass production ramp.

• Buying wafers from the foundry.

As you may have heard there is a shortage of silicon wafer foundry capacity. So you will need to make a compelling case to the foundry why they should work with you in their 5 nm or 3 nm process nodes. As you know money is a great facilitator. So it may be that you need to commit to buy wafers ahead of time with the foundry. If you commit to buy a lot of wafers ahead of time they need to provide you with direct support, preferential fabrication times (super hot lots, hot lots), etc…

Let’s say you plan on building 100,000 bitcoin miner systems. Each system containing 200 chips/ASICs inside. So that is 20,000,000 chips. In 300 mm wafers that is probably something like 5,000 wafers. The number of chips per wafer depend on your final die size, your fab yield, your package yield and your test yield. So here I assumed you get 4,000 good chips/dies per wafer. Of course these numbers could be different for your system, but I will assume these to illustrate what I think is the likely ball park. During the process phases all of these details are nailed down and adjusted as needed. The question then is what is the minimum amount of wafers the foundry would ask you to commit to buy upfront to get the kind of support and preferential access you need to get your bitcoin miners built faster.

I am going to guess a 3 nm wafer may end up costing $20,000 USD. So you see that if you end up buying 5,000 wafers that is a $100,000,000 USD purchase! Maybe you can commit to buying 10% of that upfront and get a direct deal with the foundry, maybe not, you need to negotiate.

There are also system level miner considerations.

These are outside of the scope of this article since they are not directly custom silicon items. But it’s worth briefly mentioning them since custom silicon is developed to directly support a custom system hardware project; in this case a bitcoin miner.  Here are some things that will need to be planned:

• Hiring a CM.

You need to build systems in mass production somewhere. This supplier needs to be able to source all components, assemble, test them and package them to be shipped for you. A lot of companies choose CMs in Asia (China, Taiwan, etc…). These guys will also develop some or all of your factory test infrastructure. You need to pick wisely. The same CM company has very different levels of quality and experienced personnel for different customers. If you’re a new or small customer you may not get a good team, so you need to shop around for the right CM partner.

• Pre-silicon deliverables.

  1. FPGA board. Your firmware team needs a platform to start developing code on in preparation for the first build.
  2. Blank packaged chips and mock form factor accurate PCB boards. Your mechanical engineers may need these so they can build mechanical only prototypes to mock-up the cooling solution well ahead of your first system build at the CM.

• Designing the hard system level stuff.

  1. Firmware. You’ll need to write the firmware to control the PCBs with all the ASICs on them. So you need some firmware engineers with experience writing firmware for bitcoin miners.
  2. Cooling. You’ll need to cool down your miners. These miners consume thousands of watts each. This means you’ll need to design a customized heatsink system. Some people use fans, others immersion cooling, etc… Whatever you do this is a critical part of the project and you need to hire good mechanical engineers with experience in this type of design.
  3. PCB boards. You’ll need to design efficient power supplies. There is no point in making a super power efficient custom silicon chip and then you waste lots of power in the power converter plugged to the wall feeding your chip. You’ll also need to design good PCBs with thick copper so that your board losses are not too high. This all means that you need to hire a good quality electrical engineer to design this for you.

In summary.

Likely time to first samples 14 months from kick off.

Likely time to final silicon samples 23 months from kick off.

Summary of fixed costs 26 to 29 million USD. This is for the chip only. There will be some additional costs to develop the bitcoin miner system as discussed in the system level miner considerations section.

The estimates above assume the project is run like a tight ship. This can be hard to do generally, and especially when there are a lot of people and companies working together for the first time. Without experienced people and a good process to follow the chances to execute in these timelines are greatly diminished. Managing cross functional, multi national and multi company teams is vital for this engagement.

As you can see this project is doable. It’s also a big investment with big risks that need to be mitigated. So the question is: what will be the price of bitcoin by the time you have your miners ready?

 

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Disclaimers: All prices, schedules and details in this article are my best guesses, my opinions, and what I gather from multiple sources of information. I provide this for illustration and informational purposes only. Use at your own risk. As a project progresses through the phase sign offs all these details are committed/verified with suppliers.