
RISC-V Boom CPU - rwmj
https://twitter.com/boom_cpu/status/1032447070928396289
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rwmj
"BOOM" is the Berkeley Out-of-Order Machine RISC-V processor [https://ucb-
bar.github.io/riscv-boom/](https://ucb-bar.github.io/riscv-boom/)
[https://github.com/ucb-bar/riscv-boom](https://github.com/ucb-bar/riscv-boom)

I believe this particular chip is a research chip, and the first time that
BOOM has been taped out in real silicon. Other RISC-V chips are based on the
simpler, in-order Rocket design (eg. SiFive's HiFive Unleashed FU540); or are
completely custom designs (eg. the Western Digital 32 bit chips that will soon
be appearing in a hard drive near you).

Note that most Linux distros would not run on this chip out of the box, since
the chip does not support the C-compressed extension. They would need to be
recompiled. (Of course the chip being a research project and not generally
available makes this rather theoretical)

~~~
h4b4n3r0
Seems like a waste to tape something out and not make it generally available.
Might as well make some money.

~~~
rwmj
The economics don't really work like that. These were likely built on a
multiproject process similar to TSMC CyberShuttle where you share the wafer
with many other projects to share costs. You can see _chris_ below said only a
few dozen were made. This keeps costs within the range of reasonable, although
I bet it still ended up costing thousands or tens of thousands of dollars.

Doing a run which would be vaguely profitable would require making millions of
chips and cost millions of dollars up front, and very few projects could
afford such a speculative investment.

SiFive did do a VC funded commercial run, but I bet they are not yet making a
profit on their boards even though they cost $1,000 each.

[https://en.wikipedia.org/wiki/Multi-
project_wafer_service](https://en.wikipedia.org/wiki/Multi-
project_wafer_service)
[http://www.tsmc.com/english/dedicatedFoundry/services/cyberS...](http://www.tsmc.com/english/dedicatedFoundry/services/cyberShuttle.htm)

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csense
Is there anywhere you can buy these chips? Or better yet, a dev board with RAM
/ SD / USB / networking and bootable Linux?

~~~
_chris_
Nope, just a small batch test-chip run. And even out of a few dozen chips, I
think we only did packaging for ~5 chips.

It boots Linux, but at 6 mm^2, it's not really big enough to contain an on-
chip memory controller, so going out to DRAM is through an FPGA controller and
thus is painful.

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agumonkey
$ means cache (pun on cash) ?

~~~
jburgess777
Yes, I$ and D$ are the instruction and data cache respectively.

~~~
agumonkey
fun

