[ale] Really cool new hardware

[Solomon Peachy]

On Tue, Jan 19, 2021 at 12:45:20PM -0500, jonhall80 at comcast.net wrote:
> I disagree.  I think the interest is across the board, for several reasons.

Yes, there is interest "across the board" but as I am writing this, open 
"high-end RISC-V" cores do not really exist; all but a handful [1] of 
the freely available designs are microcontroller-class.  The rest are 
either proprietary in-house designs (which may or may not have tweaks to 
the base ISA) or available to license in a manner similar to Arm's 
offerings.

[1] BOOM and the Sodor cores out of UC Berkley, intended for educational 
    purposes.

> The licensing and start-up costs were fairly high.  This prevented 
> smaller companies and institutions getting into the marketplace of 
> producing compatible ARM chips with extended capabilities.

Startup costs are the same either way; if anything they are lower for 
Arm due to the much more mature ecosystem around it.

(and "Extended capabilities" are not something you want at the ISA level 
 for a general-purpose architecture, because then you'll end up with 
 incompatibilites at both the binary and source-code level..)

> Things are different than when Intel and AMD got started.  You can 
> have easy access to FAB plants, good design tools, FOSS software and 
> crowd-funding.  But when you are working on a shoestring, paying out a 
> half-million to million dollars in licensing fees to get started is 
> daunting.  A million bucks is five good engineers for a year.

To get a custom SoC built you're looking at about a million bucks a year 
in proprietary EDA tools, plus salaries on top of that.  CPU core 
licensing fees are a drop in the overall budget -- you also have to pay 
for the rest of the SoC, and either you build it yourself or license it 
from someone else, before you ever get to implementing your "special 
sauce".  It's the classic "time to market vs money" tradeoff.

> RISC-V is allowing (encouraging? Cheering on?) an open design model 
> that allows many companies to invest in parallel.

Yep; the core ISA is royalty-free, and anyone can build a core that 
implements it.  Which is great, if you can afford to develop your own 
core (and very few can; you have to have some pretty serious volume 
before the NRE involved in going your own way eclipses the Arm licensing 
fees.. which is the secret behind Arm's success.  That said, the 
continued consolidation in the semiconductor industry has changed this 
dynamic as per-company volumes have grown massively)

> The low-power capabilities of RISC-V is also attractive.  When you 
> have 500,000 processors in a HPC system, every half-watt you save goes 
> a long way, in both direct power and cooling.

In HPC environments, it's not the "cpu core" that is sucking down the 
wattage, it's "un-core" stuff -- stuff like the memory and I/O 
controllers, plus obviously everything else connected.  RISC-V won't 
affect that at one iota at an equivalent process node and clock speed. 

This is a lesson that proponents of "high-end Arm" have also started to 
learn the hard way; it turns out that by the time you slap a couple 
hundred gigabytes of RAM across four memory busses and a several dozen 
saturated PCIe lanes onto your system, your overall "transactions per 
watt" comparison isn't quite so favorable any more.

> In a SBC that I am working on in Brazil, we switched from using 5 
> volts to power the SOC to 3 volts, and went from 10W power to 5W of 
> power used.  This actually allowed us to turn up the clock, since the 
> heat generated was lower.  So lowering the voltage and power allowed 
> the chip to run faster.

Supply voltage has nothing to do with the CPU core, and everything to 
do with the physical implementation (process node of the ASICs, power 
supply design, I/O voltage requirements, etc etc)

(BTW, my last gig was at a fabless semiconductor startup that was 
 eventually acquired by Arm. I was swimming in the deep end of 
 mixed-signal ASIC design/bringup for nearly six years)

 - Solomon
-- 
Solomon Peachy			      pizza at shaftnet dot org (email&xmpp)
                                      @pizza:shaftnet dot org   (matrix)
High Springs, FL                      speachy (freenode)
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