Re: No cache control on ppc??
On Sat, 2002-01-12 at 18:10, Siggi Langauf wrote:
> On i586 (or newer) machines with AGP, the X server can set some MTRR
> ranges. AFAIUI, these tell the (CPU-internal) cache controller not to
> cache video memory (which wouln't make any sense, as that is used
> write-only).
> While working with xine, we found that not setting these (usually because
> the kernel doesn't have MTRR support) slows video playback down,
> probalby due to "cache pollution".
Don't think so. The speedup is due to write combining, which only works
with uncached memory.
> At least on my iBook, lspci claims that the Rage Mobility is connected via
> AGP 2x, so this could be relevant.
> xine can play DVDs fine on a PII-450, so why shouldn't it on a G3-600...
True, the problem is likely the lack of write combining.
Fortunately, 4.2.0 will use DMA when DRI is enabled, which is reportedly
significantly faster (or as fast, but with less CPU load) than write
combined CPU transfers on i386. It might make the difference for an
iBook 600.
--
Earthling Michel Dänzer (MrCooper)/ Debian GNU/Linux (powerpc) developer
XFree86 and DRI project member / CS student, Free Software enthusiast
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