Re:Would you be willing to fund a Linux port to Apple Silicon?
by amluto on Sunday November 29, 2020 @11:18PM
(#25250682)
Building a useful 8-wide decode block on x86 might be extremely expensive in terms of area and power.
For a long time, we’ve been told that the nasty x86 ISA is no big deal and that a good CPU can cache decoded instructions and play other tricks to make the ISA irrelevant. But x86 really does have fundamental problems. The length of an instruction can’t be determined until the instruction is almost fully decoded, which makes deciding in parallel quite nasty. And the x86 memory model is fundamentally more expensive than ARM’s.
M1 is the first serious attempt to make a competitive high-performance non-x86 CPU. Perhaps the real lesson from M1 will be that x86 can’t compete.
For a long time, we’ve been told that the nasty x86 ISA is no big deal and that a good CPU can cache decoded instructions and play other tricks to make the ISA irrelevant. But x86 really does have fundamental problems. The length of an instruction can’t be determined until the instruction is almost fully decoded, which makes deciding in parallel quite nasty. And the x86 memory model is fundamentally more expensive than ARM’s.
M1 is the first serious attempt to make a competitive high-performance non-x86 CPU. Perhaps the real lesson from M1 will be that x86 can’t compete.