Leaked docs hint Google may use SiFive RISC-V cores in next-gen TPUs

After a difficult 2023, things may be looking up for RISC-V chip designer SiFive, which expects AI to drive strong revenue growth in 2024. According to documents obtained by Bloomberg this week, the Silicon Valley upstart's rebound will be driven by a second-gen processor designed for AI servers, or so the biz hopes. Though …

[Ace2]

“the X280's successor, the X390”

Some people actually get paid to pick modelnumbers.

[TheWeetabix]

“Just to make sure people know its a better processor….”

[Fred Daggy]

If it was REALLY better, it would go up to 11.

[Abominator]

What is there revenue model? Are they selling the designs or they selling the chips?

I don't see how they make money out of an open source CPU designs, unless there is a proprietary element to it.

Otherwise, the big tech firms can do an Amazon like when they take the open source software and then run that up as a services and change for both the hardware and managing the software.

It's why Casandra DB etc changed their licensing models. Open source but not quite.

[Anonymous Coward]

I think their plan is to assist companies with their chip designs.

Making it available for free ensures that they have “the most popular design”. If people want off the shelf - SiFive have that already.

The consultancy model will make more money.

[Charlie Clark]

I didn't know Cassandra was a CPU design…

[venneford]

The revenue model is simple: Only the instruction set is open, not the hardware implementation to process the instruction set.

The Risc-V instruction set is maintained by a foundation based in Switzerland and details what instructions can be sent to the processor and then the output from the processor for that instruction. So, if you tell the processor to "Load memory location XXX into memory register Y", the processor does that. It doesn't specify how to do it. And, if 2 different companies develop a processor using completely different circuit designs, but both processes the input and output the same, then the software developed for that architecture will be software compatible.

One of the more important parts of the Risc-V architecture is that it does allow for additional ancillary processors and extensions that can be vendor specific. Hence, SiFive's coprocessors mentioned here.

But, SiFive designs Risc-V hardware and ancillary processors for tailored solutions. They are selling hardware. They don't have to publish their processor extension or give anything away.

Now, there are open-sourced processor circuits that anyone could pull down and then send to a fabrication facility, but those are not really optimized for anything and are very rudimentary in nature.

Risc-V is attractive as ARM and Intel will charge for even access to read their instruction sets and you have to license the rights to even use those instruction sets.

[HuBo]

Very sensible approach

With Tenstorrent now shipping Grayskull PCIe cards, featuring 100 Tensix cores, each of which includes 5 RISC-V CPUs (so 500 RISC-Vs on that SOC), it makes sense to me that others (eg. Google) might be interested in coming up with some similarly tasty AI-accelerator recipe, as described in the leaked docs (eg. Coke vs Pepsi). The resulting competition should be good for the industry, and yummy for customers (IMHO).