4 ms·

If I recall correctly and shuttling instructions around fast enough is the main bottleneck right now, why do people want to return to RISC?

t-3 4y ago
Writing X86 assembly is painful, writing aarch64 or RISC-V assembly is easy and fun. That, and everything is fast nowadays. Even microcontrollers are hundreds of MHz with huge memories. There's very little pressure to increase high-end performance, a lot of pressure to make more software.
yjftsjthsd-h 4y ago
> If I recall correctly and shuttling instructions around fast enough is the main bottleneck right now, I don't think so? Aren't we still at the point in the cycle where moving data around is the bottleneck? Anyways, AIUI modern RISC does have tricks to make things more efficient if you really want, but it's not usually viewed as needed. > why do people want to return to RISC? What return? Nearly everything on the market is RISC; the one exception is x86, which is still RISC (ish) but with a CISC ISA stuck on top.
DowsingSpoon 4y ago
I think one of the main arguments in favor of RISC-V is the permissive licensing. A lot of the people moving to RISC-V are absolutely weighting this heavily in their decisions. The RISC-V folks would probably tell you that the compressed instruction set nets the same code density benefits you'd see on more complex ISAs. Myself, I haven't studied it enough to have a real opinion. RISC proponents tout its benefits for energy efficiency, which is a pretty important thing these days. Though, that might be up for debate. This paper states that "there is nothing fundamentally more energy efficient in one ISA class or the other. The ISA being RISC or CISC seems irrelevant." <https://research.cs.wisc.edu/vertical/papers/2013/hpca13-isa-power-struggles.pdf https://research.cs.wisc.edu/vertical/papers/2013/hpca13-isa...> Personally, I think the RISC vs CISC debate is just a little bit dated. The ideas behind RISC were new and exciting in the 80s. The equation had changed and there was a lot of room for innovation and improvement with sweeping changes to computer architecture. They were thinking about how instructions could be pipelined, how compilers would allocate registers, how profiling showed that seldom-used instructions can be deadweight that literally holds a system back. Then in the 90s, the equation changed again. Pentium Pro style superscalar architecture showed that you can do well with even a terrible ISA if you're able to throw enough transistors at it.

t-3 4y ago

Writing X86 assembly is painful, writing aarch64 or RISC-V assembly is easy and fun. That, and everything is fast nowadays. Even microcontrollers are hundreds of MHz with huge memories. There's very little pressure to increase high-end performance, a lot of pressure to make more software.

yjftsjthsd-h 4y ago

> If I recall correctly and shuttling instructions around fast enough is the main bottleneck right now, I don't think so? Aren't we still at the point in the cycle where moving data around is the bottleneck? Anyways, AIUI modern RISC does have tricks to make things more efficient if you really want, but it's not usually viewed as needed. > why do people want to return to RISC? What return? Nearly everything on the market is RISC; the one exception is x86, which is still RISC (ish) but with a CISC ISA stuck on top.

DowsingSpoon 4y ago

I think one of the main arguments in favor of RISC-V is the permissive licensing. A lot of the people moving to RISC-V are absolutely weighting this heavily in their decisions. The RISC-V folks would probably tell you that the compressed instruction set nets the same code density benefits you'd see on more complex ISAs. Myself, I haven't studied it enough to have a real opinion. RISC proponents tout its benefits for energy efficiency, which is a pretty important thing these days. Though, that might be up for debate. This paper states that "there is nothing fundamentally more energy efficient in one ISA class or the other. The ISA being RISC or CISC seems irrelevant." <https://research.cs.wisc.edu/vertical/papers/2013/hpca13-isa-power-struggles.pdf https://research.cs.wisc.edu/vertical/papers/2013/hpca13-isa...> Personally, I think the RISC vs CISC debate is just a little bit dated. The ideas behind RISC were new and exciting in the 80s. The equation had changed and there was a lot of room for innovation and improvement with sweeping changes to computer architecture. They were thinking about how instructions could be pipelined, how compilers would allocate registers, how profiling showed that seldom-used instructions can be deadweight that literally holds a system back. Then in the 90s, the equation changed again. Pentium Pro style superscalar architecture showed that you can do well with even a terrible ISA if you're able to throw enough transistors at it.