[Linux-fbdev-devel] Re: radeon, apertures & memory mapping

[Jon Smirl]

On Mon, 14 Mar 2005 08:52:46 +1100, Benjamin Herrenschmidt
<benh at kernel.crashing.org> wrote:
> 
> > The best model would be to chuck the AGP/PCI Express interface on the
> > board and have a hyperchannel instead. Hyperchannel provides full
> > cache consistency without all of these flushing problems. The GPU
> > really is another specialized CPU, give it a CPU class memory
> > interface.
> 
> You mean HyperTransport ? Well, PCI Express isn't far from that
> neither...

Yes, HyperTransport. That's what I get for writing email while the
babies are crying.

Does PCI Express support a full cache coherency protocol like
HyperTransport? So if the GPU touches a page of system memory, the
system memory will get flushed out of the CPU cache? In that case we
don't need to mark shared GPU/CPU memory as non-cachable.

> 
> Ben.
> 
> 


-- 
Jon Smirl
jonsmirl at gmail.com