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The increased instruction set included in AVX-512 would hopefully stay though, even if the 512 wide processing unit goes away.
by yxhuvud 5y ago
The increased instruction set included in AVX-512 would hopefully stay though, even if the 512 wide processing unit goes away.
- phkahler 5y agoTo keep the instructions also means keeping the extra wide registers. Not sure how big a deal that is. I suspect the wider vector registers aren't such a big deal but there are also twice as many of them. The old AMD strategy of running a 4-element vector through 2 units of half size (or sequentially through one unit of half size) could work but the increased register set is still a burden to some extent.
- kimixa 5y agoMy understanding is that for general purpose registers, register renaming and other hazard-avoiding optimisations means that the register file is significantly larger than the total of (register width * number of registers). Do the SIMD units have similar register duplications? If so, reducing the duplication count would do pretty much that (Reducing the area at the cost of lower performance). Even if not, the large general purpose register duplication count likely means that the SIMD registers are actually a lower proportion of the register file on chip than the register width would imply, making it less of a saving. But generally I agree, I'm much more interested in the extra instruction vocabulary and things like masking lanes than the increased register width. I also wonder at what point the cut off of when a use case would be worth pushing to a more dedicated accelerator (like a dsp or gpu).