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by nickpsecurity 478 days ago
You should really look into summaries on how deep sub-micron adds more problems as processes shrink. It's crazy that 28nm and under even work at all. They also break faster in more ways than larger, mature nodes.

Far as 130nm, I'll give you a few reasons I'd use one over a 7nm FPGA. This is a non-HW guy saying what he's heard from pro's at different times. HW people, feel free to correct me about whatever I get wrong.

1. Unit prices. If you can take the upfront cost (NRE), the per unit price will be much lower than FPGA's. You might charge plenty per unit depending on the market. This can be a source of profit.

2. Older, larger nodes are said to be better for analog. Lots of designs are mixed-signal to use analog for it's lower power, extra performance, or how it doesn't blink (no rise/fall with clock).

3. ASIC's can't be reprogrammed like FPGA's. The custom design might be more secure like Sandia Secure Processor (Score) or CHERI RISC-V. FPGA's can only do one of these except for antifuse FPGA's.

4. Larger nodes are easier to visually inspect for backdoor with cheaper, teardown hardware. Who knows what's in the FPGA's.

5. Larger nodes are easier to synthesize, P&R, and auto-inspect (eg Calibre). That means open-source tools have a better chance of working or even being developed.

6. If not too power hungry (or power is cheap), some applications can let you outperform 7nm parts with parallel use of 130nm parts which are much cheaper or highly-optimized. An example what media wanting to do distributed, massively-parallel design for doing NN training maybe with 8-bitters and on-board, analog accelerators. My inspiration, aside from old MPP clusters (eg Thinking Machines), was a wafer-scale, analog NN done before Cerebras.

7. Improved reliability in general. In trusted checkers or fault-tolerant configuration, I feel like the 130nm parts are less likely to have a double failure or fail before the 7nm nodes.

8. If there's a business case, saying you built your own hardware is cool. It might even attract talent who benefit the company in other ways.

That's off the top of my head. Again, I just read a lot of stuff on ASIC's.

On a side note, you might find eASIC's Nextreme's interesting. They're Structured ASIC's that work like FPGA's in that design gets put on something with pre-made blocks to save money. Except, instead of software programmed, some via or metal layers get customized for the routing. While that reduces NRE cost, doing the routing in hardware supposedly reduces unit prices and energy maybe with a performance boost. They used to sample chips out quickly and relatively cheaply. Also, I think Triad Semiconductor had S-ASIC's with analog stuff.

2 comments

eASIC Nextreme sounds like a good ol' fashioned ULA (uncommitted logic array), the sort of thing that's at least as old as the Sinclair ZX81 (where it drove the per-unit cost through the floor).
I hadn't heard of that. Looking it up, it's a type of gate array which I believe inspired both S-ASIC's and devices like FPGA's. Here's an intro to each for those following along:

https://en.m.wikipedia.org/wiki/Gate_array

http://eda.ee.ucla.edu/EE201A-04Spring/ASICslides.ppt

I also found a link with the pricing of one. It was $45,000 for 45 prototypes on 45nm through eASIC.

https://www.design-reuse.com/news/25107/easic-45nm-asic-valu...

That put having chips made into the realm of possibilities for even a small business. Other costs might prevent that but I could see more stuff opening up. I also envisioned hard blocks done on those nodes for common components so the S-ASIC was used for custom logic (eg differentiators).

Thanks! Yeah, for analog the case is obvious, both because there's no such thing as an analog FPGA and because smaller feature size comes with big drawbacks for analog; that's why I said, "why would you fab a digital design in 130nm". The others I'm less sure about, but they do sound plausible.
Yeah, there have been a dozen different attempts to make "an FPGA, but analog". This is one of them. They all failed. You'll note the page hasn't been updated since 02006: https://web.archive.org/web/20060715013941/http://www.anadig.... Analog circuits aren't fungible the way digital circuits are.

I'm not saying it's not a worthwhile research direction, just that it hasn't borne commercially viable fruit so far, despite decades of attempts.