By: Linus Torvalds (torvalds.delete@this.linux-foundation.org), July 13, 2013 2:11 pm
Room: Moderated Discussions
Michael S (already5chosen.delete@this.yahoo.com) on July 13, 2013 1:13 pm wrote:
>
> Wait. You will see how Silvermont can't keep its 128b-wide execution units even half-busy and how Jaguar,
> that also has 128b-wide execution units runs circles around Silvermont happily executing AVX code paths.
We'll see. I still don't see the actual loads that even use it to begin with being really all that relevant. Intel does seem to agree with me (for once - I have *not* been impressed by their Atom efforts so far), and while you are quite likely right about Jaguar beating Silvermont on FP, I would have pointed to the OoO FP unit rather than AVX.
But more importantly, I think it will all be entirely irrelevant. Because all that matters is the integer side. And it will be interesting to see how Silvermont-vs-Jaguar plays out there (especially wrt "similar power" vs "similar price" space. At the high end of Jaguar you won't be comparing against Silvermont).
Which is kind of my point. In the higher end, you actually have Haswell (10W? 7W? Whatever the "big tablet" space is). You need to think about what Silvermont is aimed at. Low power. High-performance FP just isn't even in the cards.
> > So why are you so convinced AVX makes sense?
>
> Not for the reasons I stated above.
> But because it makes programmers (mine) life easier.
Sure. And you'll have to make AVX be a conditional path. In the kind of market where Atom is relevant, you need to do that. Ask yourself how important the small tablet, cellphone and microserver market is..
Linus
>
> Wait. You will see how Silvermont can't keep its 128b-wide execution units even half-busy and how Jaguar,
> that also has 128b-wide execution units runs circles around Silvermont happily executing AVX code paths.
We'll see. I still don't see the actual loads that even use it to begin with being really all that relevant. Intel does seem to agree with me (for once - I have *not* been impressed by their Atom efforts so far), and while you are quite likely right about Jaguar beating Silvermont on FP, I would have pointed to the OoO FP unit rather than AVX.
But more importantly, I think it will all be entirely irrelevant. Because all that matters is the integer side. And it will be interesting to see how Silvermont-vs-Jaguar plays out there (especially wrt "similar power" vs "similar price" space. At the high end of Jaguar you won't be comparing against Silvermont).
Which is kind of my point. In the higher end, you actually have Haswell (10W? 7W? Whatever the "big tablet" space is). You need to think about what Silvermont is aimed at. Low power. High-performance FP just isn't even in the cards.
> > So why are you so convinced AVX makes sense?
>
> Not for the reasons I stated above.
> But because it makes programmers (mine) life easier.
Sure. And you'll have to make AVX be a conditional path. In the kind of market where Atom is relevant, you need to do that. Ask yourself how important the small tablet, cellphone and microserver market is..
Linus