4 ms·
While the width of units is indeed 256, certain operations like shuffles have special treatment so it is more like hybrid design that focus on efficiency. In re
by neonsunset 3y ago
While the width of units is indeed 256, certain operations like shuffles have special treatment so it is more like hybrid design that focus on efficiency. In reality, it works quite good and better instruction density per bytes processed leads to sometimes even less energy consumption when a certain path is upgraded to AVX512 from AVX2.
And as the sibling comment mentions, AVX512 is not just about the width but also about newer instructions available at 128b and 256b widths as well under AVX512VL.
- adrian_b 3y agoAMD has four 256-bit execution units, which are ganged into two 512-bit execution units. Intel has only three 256-bit execution units, which are also ganged into two 512-bit execution units, by adding an extra 256-bit unit, which stays idle in 256-bit mode. So the throughput for most register-register 512-bit operations is the same for Intel and AMD, except that AMD has a single FP64 multiplier vs. two FP64 multipliers on Intel and that the path to the L1 cache has double width on Intel (while AMD does one 512-bit load per cycle + one 512-bit store every other cycle, Intel can do two 512-bit loads from L1 + one store per cycle).