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RISC-V: They Should Have Known Better

dmitry.gr

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Re: RISC-V: They Should Have Known Better

#21

Post by tsukikage »

hn_submit wrote: post #16

Why is he complaining about everything being optional in RISC-V? Isn't that the whole idea of RISC-V? The market can sort it out for themselves. RISC-V is already dominant in the MCU space despite its flaws, and many of them will be solved in due time. Most MCUs are used for dead-simple solutions, like electric blankets and microwaves with segment displays or LEDs. Whether their interrupts are handled in 44 or 22 cyc…

He explains, at length: there is no sane way to determine what the hardware you are running on actually supports, and so there is no sane way to ship compiled code that is both compatible and performant.

We already had the mystery meat CPU wars several decades ago. We know how to make sane ISAs now and should be past that.

Re: RISC-V: They Should Have Known Better

#23

Post by kjs3 »

ethin wrote: post #13

I can definitely see his argument, although I still do believe RISC-V did a lot of things better than x86... I really do hope that the arch is eventually able to fix this. Better that there be an open ISA than them all be closed IMO.

Yeah...risc-v can learn from 50 years of x86 (among others). And yet.......

Re: RISC-V: They Should Have Known Better

#25

Post by IshKebab »

__d wrote: post #11

So … use RISC-V as the strawman, and create a community-based RISC-6 that doesn’t have these weaknesses? Better to get in now before it becomes too solidly entrenched.

Likely impossible unless you somehow come up with something vastly better (unlikely).

None of these things are remotely bad enough to make the downsides of using another ISA palatable.

Re: RISC-V: They Should Have Known Better

#26

Post by walrus01 »

hn_submit wrote: post #16

Why is he complaining about everything being optional in RISC-V? Isn't that the whole idea of RISC-V? The market can sort it out for themselves. RISC-V is already dominant in the MCU space despite its flaws, and many of them will be solved in due time. Most MCUs are used for dead-simple solutions, like electric blankets and microwaves with segment displays or LEDs. Whether their interrupts are handled in 44 or 22 cyc…

> The market can sort it out for themselves

Because nobody will write software for 300 unique hardware variations of a platform that have inconsistent capabilities. Consistency is one of the reasons why x86-64 with extensions like like SSE, AVX2 etc is popular.

Re: RISC-V: They Should Have Known Better

#27

Post by hn_submit »

tsukikage wrote: post #21
hn_submit wrote: post #16

Why is he complaining about everything being optional in RISC-V? Isn't that the whole idea of RISC-V? The market can sort it out for themselves. RISC-V is already dominant in the MCU space despite its flaws, and many of them will be solved in due time. Most MCUs are used for dead-simple solutions, like electric blankets and microwaves with segment displays or LEDs. Whether their interrupts are handled in 44 or 22 cyc…

He explains, at length: there is no sane way to determine what the hardware you are running on actually supports, and so there is no sane way to ship compiled code that is both compatible and performant. We already had the mystery meat CPU wars several decades ago. We know how to make sane ISAs now and should be past that.

You don't need to probe what hardware you're running on because you know being the manufacturer. The code is bespoke for your solution and nothing more. No foreign code is going to run on it.

Different problems require different solutions. An electric blanket doesn't need a barrel shifter for multiplication or even floating point hardware. The ISA can change depending on what's needed to solve a particular problem, not to provide an "one size fits all" solution.

Re: RISC-V: They Should Have Known Better

#28

Post by kjs3 »

kev009 wrote: post #9

It's basically MIPS all over again The conclusion is honest, and you can of course brute force any ISA into any role. I used to loathe x86 for that reason, but now that I'm older I respect the game.

I think MIPS is a great example, and even there I don't think there's the bizarre bifurcation of ISA options RISC-V brings to the table.

As a fellow olderster, I can't help but think that after almost 50 years of "ISA X is sooooo much better than x86 it's obvious ISA X is the future and x86 will be dead Real Soon Now (for whatever todays version of x86 is)" I can only shake my head ruefully and say "ping me when that happens".

Controversial Take (that history proves isn't): Software matters; ISAs don't.

Re: RISC-V: They Should Have Known Better

#29

Post by NetMageSCW »

exmadscientist wrote: post #14

> After being asked for the Nth time to explain, I decided to put it all down in one place so that I could simply link to it when asked next. Bookmarked, because I've needed the same. The worst part of all this is that they really should have known better by now. In 1980 you could make these kinds of mistakes, because this was pretty new territory. In 2020, doing this just makes you stupid. Or ignorant. Or both.

I’m not so sure - the 6502 existed in 1980 and showed the way.

Re: RISC-V: They Should Have Known Better

#30

Post by NetMageSCW »

IshKebab wrote: post #20

I think a lot of this criticism is completely true. However it's also overblown. I do think the ISA matters, but little mistakes like these definitely don't matter enough to preclude making M-series class chips. The reason it hasn't happened yet is simply time. It takes a really really long time to build up to that level of performance. They've definitely gone overboard on the optionality stuff though. I don't think…

I don’t think making optional what optional features are available is a little mistake. It is a torpedo to the waterline.
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