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David Kanter on PCPer talking about Zen architecture


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Well, it won't be able to run XTU since that's an Intel application.


But you will see the difference in benchmarks such as Y-cruncher and HWBOT x265 1080P/4K


It will be interesting to see whether Zen runs faster with 128-bit AVX vs. 256-bit AVX. For the Bulldozer family, it was the former. (Though Carrizo had 256-bit AVX pulling almost even with 128-bit.)


It's also worth mentioning that Zen opts for separate FP-Add/FP-Mul instead of a native FMA. Zen's FP-Add and FP-Mul throughput is theoretically on par with Intel (under optimal conditions). But FMA will be half throughput and the same as the Bulldozer family.


This is the first time I've heard of a processor that has a "slow" FMA. Everything else, Bulldozer, all Intel, even PowerPC - if it has an FMA, it has a fast FMA. And it *only* has FMA. FP-Add is just (A * 1 + B). FP-Mul is (A * B + 0). So all floating-point arithmetic is the same (in cost) whether it be FP-Add, FP-Mul, or FMA.


This presents a problem for y-cruncher because all the FMA that is uses was done assuming it has equal cost as everything else. So I'm half expecting Zen to be better off with some of the older Sandy Bridge code - with possible modifications like narrowing down 128-bit AVX.


Zen coming on March 2nd *should* give me enough to do get the hardware and get a Zen-optimized binary out in time for Pi Day (March 14th).

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@Mysticial send me an email with instructions what you need to get Y-cruncher ready for Zen :)


Massman has chosen not to receive private messages or may not be allowed to receive private messages. Therefore you may not send your message to him/her.


If you are trying to send this message to multiple recipients, remove Massman from the recipient list and send the message again.


I'll send you an email when I get home.

Edited by Mysticial
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