AMD Van Gogh Ultra-Low Power Processors

Re:AMD Van Gogh Ultra-Low Power Processors by zibzab on Friday April 30, 2021 @04:43AM (#26991116)

I have 4 issues with your comment:

1. AMD and apple use different methods for measuring effect. So AMD 35W and apples 18W are not directly comparable.

2. Despite what HN top posts want you to believe newset Zen3 has a performance advantage over M1. Hence at this point it make sense to concentrate on reducing power usage.

3. AMD64 is basically internally a RISC.

4. Why does _any_ post on _anything_ quickly turns into praising apple? You are stealing attention from the real discussion.

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Re:AMD Van Gogh Ultra-Low Power Processors by Const-me on Friday April 30, 2021 @09:40AM (#26993331)

Good comment except this:

> 3. AMD64 is basically internally a RISC.

They decode some rarely used instructions into multiple micro-ops, but these micro-ops can be very complex still. Example:

    vfmadd231ps ymm1, ymm2, ymmword ptr [rsi + 4*rcx + 96]

The above instruction computes quite a lot of stuff (first the read address, then 8-wide multiply+add), yet on most modern CPUs including AMD Zen 2 it decodes into a single micro-op.

More often the opposite happens, AMD64 instructions are merged into a single micro-op, this is called macro-op fusion.

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