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SiFive Tapes Out First 5nm TSMC 32-bit RISC-V Chip with 7.2 Gbps HBM3

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Re: SiFive Tapes Out First 5nm TSMC 32-bit RISC-V Chip with 7.2 Gbps HBM3

#11

Post by StringyBob »

snypher wrote: post #6
klelatti wrote: post #2

How did SiFive get anywhere near 5nm TSMC?

"The tape out means that the documentation for the chip has been submitted for manufacturing to TSMC, which essentially means that the SoC has been successfully simulated. The silicon is expected to be obtained in Q2 2021." Would this mean the actual chip delivery may still be delayed?

Chip manufacturing has many steps. For a new leading edge process it may take 3-6 months to get silicon back after submitting the design to a silicon foundry for manufacturing.

For a small volume ‘shuttle’ run hopefully there won’t be delays, but this is not the same as having working chips!

The foundry will do initial checks it is manufacturable at ‘tapeout’ when you submit your design, but you don’t know for sure if your chip works with intended functionality until you get it back! You are relying on lots and lots of simulations up front before your ‘tape-out’.

Sometimes issues are found and a chip requires a re-spin - basically another go with the bugs fixed. You want to do this as few times as possible (ideally right first time) due to cost and time of these iterations.

Re: SiFive Tapes Out First 5nm TSMC 32-bit RISC-V Chip with 7.2 Gbps HBM3

#12

Post by lizknope »

klelatti wrote: post #2

How did SiFive get anywhere near 5nm TSMC?

They pay money just like any other customer of TSMC. SiFive has a lot of buzz in the industry. I wouldn't be surprised that TSMC wanted to work with them.

But there are other intermediary companies that help startups group multiple chips from multiple companies together into a single mask. This is called a "shuttle" and allows the companies to split the costs of the masks (I've heard up to $30 million for 5nm)

SiFive is probably building about 2,000 of these chips for development boards. They aren't trying to order a hundred million like Nvidia.

Re: SiFive Tapes Out First 5nm TSMC 32-bit RISC-V Chip with 7.2 Gbps HBM3

#14

Post by zibzab »

zozbot234 wrote: post #13

IIRC, 32-bit RISC-V is only intended for deep embedded workloads, with 64-bit for general purpose compute. So a SoC w/ a single 32-bit core would seem to be a less-than-ideal fit for the cutting-edge 5nm process.

Yeah, this seems like an odd move to me.

For this kinda of applications the static leakage of the newer & smaller node will probably hurt rather than help.

Re: SiFive Tapes Out First 5nm TSMC 32-bit RISC-V Chip with 7.2 Gbps HBM3

#15

Post by zibzab »

lizknope wrote: post #10
ohazi wrote: post #3

I know they're separate lines and capacity is sold well in advance and all that, but this chip shortage still baffles me. A startup can tape out a 5 nm chip, but STMicroelectronics can't make any of their 40-130 nm microcontrollers for the next year? Also car companies are supposedly the culprit, even though their volume is only in the low tens of millions per year, and the dustup is apparently over only six months o…

I'm in the semiconductor company. I don't really understand your question. Anyone can start a company and tape out a chip even in 5nm. My previous startup did something similar. We used an intermediate company between us and TSMC that specifically works with smaller companies. They (or TSMC) will bundle together 4 to 20 chips into a common mask as a "shuttle" run. Shuttle runs are really only used to get samples for…

Sounds like OSH Park for silicon...

Anyway, I'm still not sure why SiFive is doing this. Seems like a waste of money even as a prototype

Re: SiFive Tapes Out First 5nm TSMC 32-bit RISC-V Chip with 7.2 Gbps HBM3

#16

Post by variaga »

zibzab wrote: post #15
lizknope wrote: post #10

Earlier quoted context omitted.

I'm in the semiconductor company. I don't really understand your question. Anyone can start a company and tape out a chip even in 5nm. My previous startup did something similar. We used an intermediate company between us and TSMC that specifically works with smaller companies. They (or TSMC) will bundle together 4 to 20 chips into a common mask as a "shuttle" run. Shuttle runs are really only used to get samples for…

Sounds like OSH Park for silicon... Anyway, I'm still not sure why SiFive is doing this. Seems like a waste of money even as a prototype

SiFive is in the business of selling IP cores and back-end implementation services. The gold standard for IP core validation is "silicon proven" i.e. that it's not just a nice theoretical design on paper, but someone has actually turned it into a physical chip and tested the real life performance.

Lots of people will try to sell you their designs and services. Picking the wrong ones can waste millions of dollars and months/years of time.

The money spent on this a prototype buys SiFive credibility for both aspects of their business (assuming the chip works) - "we were able to do this for ourselves, so you know we'll be able to do it for you".

So it's not a waste, it's a marketing expense, and a necessary one.

Re: SiFive Tapes Out First 5nm TSMC 32-bit RISC-V Chip with 7.2 Gbps HBM3

#17

Post by variaga »

bravo22 wrote: post #7
ohazi wrote: post #3

I know they're separate lines and capacity is sold well in advance and all that, but this chip shortage still baffles me. A startup can tape out a 5 nm chip, but STMicroelectronics can't make any of their 40-130 nm microcontrollers for the next year? Also car companies are supposedly the culprit, even though their volume is only in the low tens of millions per year, and the dustup is apparently over only six months o…

A lot of chips are made on mature fab lines because they don't need the performance of 5nm lines or can't justify the mask costs. No one is investing in mature fab lines because they're not leading edge and they're being run to amortize the initial investmnet made into them years ago. Therefore not much additional capacity for mature lines. So yes you can see 5nm chips being taped out but the 40-130nm chips are squee…

Your point is valid, but this is almost certainly a shuttle run, so it won't be even one full wafer.

Re: SiFive Tapes Out First 5nm TSMC 32-bit RISC-V Chip with 7.2 Gbps HBM3

#18

Post by ohazi »

Kliment wrote: post #9
ohazi wrote: post #3

I know they're separate lines and capacity is sold well in advance and all that, but this chip shortage still baffles me. A startup can tape out a 5 nm chip, but STMicroelectronics can't make any of their 40-130 nm microcontrollers for the next year? Also car companies are supposedly the culprit, even though their volume is only in the low tens of millions per year, and the dustup is apparently over only six months o…

This is an extremely low volume prototype run. You can get those scheduled on short notice. Fabs love them because they can do process optimization using them, without impacting production customers. They're ridiculously expensive per-die and you commit to accept a much higher failure rate than normal. ST can and is making microcontrollers. It's just that they've sold their production for a year ahead, before it's ev…

> Fabs love them because they can do process optimization using them, without impacting production customers.

I didn't realize that, but it makes a lot of sense. I assumed that they acted more like the downstream manufacturers that I'm used to dealing with, that don't even want to talk to you unless they think you're going to place a huge order.

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