The masks alone are single digit millions, but with all the design tools and staff costs typically tens of millions is the benchmark number for a tape out in this node. After coming out of the fab, the chips go through probing, packaging and reeling.
Can you share something about the subsequent per-chip manufacturing costs?
Rule of thumb is that a processed wafer from 28nm and older is around $3k/wafer and the cost goes up kind of exponentially towards the smaller nodes. Also, in general, the fab wants you to order a "FOUP" of wafers at a time - that's 25 wafers at a go.
Great work on the chip, I’m really onboard with the trusted computing aim! Is there a way to bootstrap binary code into the reram? I’m thinking being able to ‘hand-type’ in a few hundred byte kernel rather than use a flashing tool
The chip comes from the factory with a boot0/boot1 chain that is fully reproducible and buildable from source. Developers can replace boot1 with their own version, where you could add the feature you're thinking about.
Why the few closed-source components on the system? You mention the bus, USB PHY etc -- are those things harder to design than the CPU core?
In general, things that are not strictly digital (PHYs, regulators, PLLs, ADCs) contain significant amounts of foundry IP that would be hard to release as open source. But also, some parts of the chip, for example the AXI bus fabric, were licensed simply as a risk reduction measure. If the bus fabric is bad, you've wasted millions of dollars on a mask set with little recourse. I tried to pull in some open source AXI fabrics and it wasn't pretty...a lot of rework required and even then still some bugs made it through to tape-out. Over time more and more of this can be opened but it all takes time, money, and people willing to do it.
Wait a minute, why can't I reply to bunnie's top-level comment? Anyway, here's what I wanted to say: Adding your CPU to another company's silicon is a genius move, well done. I wonder why companies don't sell their spare die space to others, is it because of trust/risk?
Crossbar is unusual to start with in that they wanted to do open RTL - so for starters, there's to a first order no companies even willing to discuss open RTL designs. Beyond that - mainly risk. I had to pinky swear that whatever I added would not break the chip, cause timing closure issues, delay the schedule, consume too much area or power, impact yield, I had to run my own validation and review program while meeting their dev methodology, etc. etc. I had to exercise an enormous amount of self-restraint to not push harder and do more interesting things as it was. It's very hard to build up inter-personal trust, and they had to take a calculated risk letting a schmuck like me potentially foul up a multi-million dollar mask set. Hats off to them for making that bold decision, it would have been easier to say nope, too risky, no benefit, cut it from the code base.
> Those with a bit of silicon savvy would note that it’s not cheap to produce such a chip, yet, I have not raised a dollar of venture capital. I’m also not independently wealthy. So how is this possible? What kind of order of magnitude of cost are we talking about? What are the next steps - is there some service to cut the wafer and put into a package for you?
The masks alone are single digit millions, but with all the design tools and staff costs typically tens of millions is the benchmark number for a tape out in this node. After coming out of the fab, the chips go through probing, packaging and reeling.
> The masks alone are single digit millions,
Ah, another reason why hardware erratas get fixed so rarely (I assume - along with retesting of course).
bunnie your book "Hacking the XBox" taught me how to get started on reversing electronics, took the fear out of the process, and replaced it with fun. Thanks for the multi-decades long effort you've made to make these tools available and accessible and approachable, your contributions to the hacker community are immeasurable and I cannot say thank you enough. Thanks man!
Thank you for sharing! Comments like this make all the effort worthwhile. <3
Why the few closed-source components on the system? You mention the bus, USB PHY etc -- are those things harder to design than the CPU core?
In general, things that are not strictly digital (PHYs, regulators, PLLs, ADCs) contain significant amounts of foundry IP that would be hard to release as open source. But also, some parts of the chip, for example the AXI bus fabric, were licensed simply as a risk reduction measure. If the bus fabric is bad, you've wasted millions of dollars on a mask set with little recourse. I tried to pull in some open source AXI…
Can I ask how bad it is with lower speed I/O? Less than 20Mbaud, so RS232, RS485, CAN, USB PD/Type-C, 10base-T, ...? The transceivers are rarely integrated, do they need different processes or do they just prefer flexible I/O pins or ...?
Wait a minute, why can't I reply to bunnie's top-level comment? Anyway, here's what I wanted to say: Adding your CPU to another company's silicon is a genius move, well done. I wonder why companies don't sell their spare die space to others, is it because of trust/risk?
Crossbar is unusual to start with in that they wanted to do open RTL - so for starters, there's to a first order no companies even willing to discuss open RTL designs. Beyond that - mainly risk. I had to pinky swear that whatever I added would not break the chip, cause timing closure issues, delay the schedule, consume too much area or power, impact yield, I had to run my own validation and review program while meeti…
Yeah, true, it's all downside for them for this, basically. Still, there must be some price for which companies will let other companies use die space, but maybe that price is higher than just doing the thing yourself...