Re: Audio Units and OpenCL?
Re: Audio Units and OpenCL?
- Subject: Re: Audio Units and OpenCL?
- From: Ian Kemmish <email@hidden>
- Date: Wed, 9 Sep 2009 21:20:05 +0100
On 9 Sep 2009, at 19:05, Richard Dobson
<email@hidden> wrote:
But Apple is in a unique position in this respect given it has in
principle full control over both hardware and software, and has an
obvious interest in supporting audio. We clearly need some kind of
heterogeneous computing solution to give us both serial and parallel
power with tight deadlines.
Well, no, not really. Since Apple have chosen to sell general purpose
computers, they have sensible opted for a symmetric multiprocessing
architecture. Intel's boffins have spent a lot of man years producing
SMP processors that run fast, and one of the key assumptions that lets
SMP multi-CPU systems run fast is that all the tasks are independent
of each other. So synchronising is an expensive operation. Not
because of how the OS is written, but because of how the chips work.
Same thing with GPUs, only more so. The graphics pipeline is very
long, and the path from graphics memory back to main memory often very
convoluted and slow. Think how many times you do a screen grab, and
think how unhappy you'd be if the GPU designer spent lots of gates and
money optimising that particular pathway. No, synchronising with a
GPU is likely to be even more expensive than synchronising with
another CPU.
Such as an audio equivalent to the GPU,
tightly coupled with the rest of the chipset. That must have
attractions
for those financial folk at the very least. I had hoped that OpenCL +
Snow Leopard were going to be pretty close to that, but seemingly not.
Well, that's asymmetric multiprocessing. It has a narrower set of
useful applications, so it's never been as popular. Mostly in
embedded systems. The good news is that synchronising is a relatively
cheap operation because you have one master CPU and lots of slaves;
the bad news is that you have to handle all the synchronisation issues
yourself.
If you want to play with an AMP architecture, you can buy a
commoditised UNIX development system quite cheaply. It's called a
Playstation 3.
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Ian Kemmish 18 Durham Close, Biggleswade, Beds
SG18 8HZ
email@hidden Tel: +44 1767 601361 Mob: +44 7952
854387
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