https://github.com/corsix/amx indicates that Apple's AMX supports up to 64-bit FP, but I don't see any performance metrics. They also have the ANE, which is the low-precision ML-focused accelerator.
> I wonder why haven’t Apple exposed it to programmers, or implemented a BLAS library on top of that thing?
Using the Accelerate framework (which includes Apple's BLAS) is the only supported way for programmers to access the AMX. Reverse engineering the instruction set to access it directly is discouraged, because it's not a documented stable interface.
It’s because Apple’s AMX was an early, in-house built version of what was eventually released by Arm as SME. Apple adopted SME in the M4 and dropped AMX, but as long as you were using their Accelerate framework instead of directly writing AMX code (which they told people not to do), you wouldn’t notice.
Now that they’re using “standard” SME, it shouldn’t be a problem to write SME assembly opcodes directly, although I suspect Apple themselves is still probably sparse on the documentation. I’m not aware if there’s any way to use intrinsics or something slightly higher level than inline-ASM, but lower level than the Accelerate framework.
The Apple’s version is indeed interesting. I wonder why haven’t Apple exposed it to programmers, or implemented a BLAS library on top of that thing?