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you don't start by designing high performance chips! You start with small embedded cores and work your way up. I disagree. For example, the first PowerPC was p

by wmf 2y ago

you don't start by designing high performance chips! You start with small embedded cores and work your way up. I disagree. For example, the first PowerPC was pretty fast and went into flagship products immediately. Itanium also went directly for the high end market (it failed for unrelated reasons). RISC-V would be much better off if some beastly chips like Rivos were released early on.

snvzz 2y ago
The high end requires specifications that were not available until RVA22 and Vector 1.0 were ratified. First chips implementing these are starting to show up as seen in e.g. MILK-V Jupiter, which is one of the newest development boards in the market. With the ISA developed in the open, the base specs microcontrollers can target would naturally tend to be be ratified first, and thus microcontrollers would show up first. RVA22+V were ratified November 2021. With the ISA developed inside working groups involving several parties, some slowness would be unavoidable, as they all need to agree on how to move forward. Thus the years of gap until RVA22+V from the time the privileged and unprivileged specs were ratified (2019). RVA23 has just been ratified. This spec is on par with x86-64 and ARMv9, feature-wise. Yet hardware using it will of course in turn take years to appear as well.
- bhouston 2y ago
  Isn't the problem the lack of advanced features for executing the current ISA with speed? I thought RISC-V chips seen in the wild do not pipelining, out-of-order, register renaming, multiple int/float/logic units, speculation, branch predictors, multi-tier caching, etc. The lack of speed isn't really related to a few missing vector instructions.
  - monocasa 2y ago
    There's a lot of cores that do all of that. Most cores are pipelined; it is RISC after all. There are quite a few superscalar cores, even a c906 is superscalar. The c910/c920 is an OoO, renaming core, with speculation. What they're lacking is area and power. A ROB with six entries is not going to compete with a ROB of six hundred entries.
IshKebab 2y ago
The first PowerPC chip was introduced in 1992! Itanium was in 2001, wasn't a from-scratch design and was famously a disaster! Not really comparable.

by wmf 2y ago

snvzz 2y ago

The high end requires specifications that were not available until RVA22 and Vector 1.0 were ratified. First chips implementing these are starting to show up as seen in e.g. MILK-V Jupiter, which is one of the newest development boards in the market. With the ISA developed in the open, the base specs microcontrollers can target would naturally tend to be be ratified first, and thus microcontrollers would show up first. RVA22+V were ratified November 2021. With the ISA developed inside working groups involving several parties, some slowness would be unavoidable, as they all need to agree on how to move forward. Thus the years of gap until RVA22+V from the time the privileged and unprivileged specs were ratified (2019). RVA23 has just been ratified. This spec is on par with x86-64 and ARMv9, feature-wise. Yet hardware using it will of course in turn take years to appear as well.

bhouston 2y ago
Isn't the problem the lack of advanced features for executing the current ISA with speed? I thought RISC-V chips seen in the wild do not pipelining, out-of-order, register renaming, multiple int/float/logic units, speculation, branch predictors, multi-tier caching, etc. The lack of speed isn't really related to a few missing vector instructions.
- monocasa 2y ago
  There's a lot of cores that do all of that. Most cores are pipelined; it is RISC after all. There are quite a few superscalar cores, even a c906 is superscalar. The c910/c920 is an OoO, renaming core, with speculation. What they're lacking is area and power. A ROB with six entries is not going to compete with a ROB of six hundred entries.

IshKebab 2y ago

The first PowerPC chip was introduced in 1992! Itanium was in 2001, wasn't a from-scratch design and was famously a disaster! Not really comparable.