[openbeos] Re: app_server: MMX/SSE help wanted
- From: "François Revol" <revol@xxxxxxx>
- To: openbeos@xxxxxxxxxxxxx
- Date: Sun, 08 Aug 2004 17:22:42 +0200 CEST
> > Well, that's nice of you two to go looking for outside help without
> > even
> > checking with the person who has written most of the graphics code.
> > BTW,
> > Francois hit the nail on the head. First we worry about getting
> > stuff
> > working and checking our current performance. After that, we can
> > consider
> > using non-portable optimizations where needed.
> It bothers me that simply asking for information has generated this
> kind of response. I don't recall getting this reaction when I asked
So is the troll :)
> around what is involved in hardware-accelerated OpenGL. To quote from
Probably noone was reading at that time :)))
> the Book of Phipps, "Premature optimization is the root of all evil."
> :D I did Google around for some info on them, but what I found was an
> explanation of what the instructions were, which is not what I
> needed.
> What I personally am looking for is *basic* information about this
> kind
> of thing. What are these instructions used for?
They are used for working with multiple wide datas, like when you have
to do something very specific to a bunch of bytes repeatively.
Like colorspace transform, FFT, ... but you can do a lot of stuff.
ffmpeg uses it for colorspace changes, and fft at least.
I think it's a bit of an always wanted RISC instruction set for x86 :)
It lets you do the same operation on several registers at once, like
mm0 += mm1; and mm2 += mm3; at the same time, and so on.
> Why are they so
> supposedly cool? How is using them better than just using the regular
Because intel's pink dressed buys said so.
> instruction set cooked up by Intel? Why does it seem that they are
> most
Because it's supposedly faster for handling streams of data.
> often associated with graphics? Can't they be used with other things,
because graphics always need a lot of bandwidth, and we need to apply
effects on a lot of pixels at once. but you can apply those to audio as
well.
I think R5's optimised memcpy() uses it as well.
> too? That kind of thing. With my being self-taught, there are a great
> many things in computer science that I just don't know about. I only
Well I don't think universities tell much about mmx anyway :p
It's just about finding the good info source.
> know *this* much about assembler, for example, and I was not aware
> that
> Gabe -- or anyone else, for that matter, -- has or had any experience
> /
> expertise with this, and so I asked. In any event, I would like to
> say
> that I don't want this to turn ugly. :)
François.
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