[MPlayer-dev-eng] DMA or not DMA

[James Lancaster]

> 
> Well, if northbridge bandwidth is the issue, you could get a dual
> pentium at a lower clock rate and achieve speedup at lower cost.
> 

If that is the problem, using dual pentiums may well increase the problem, 
because on Intel SMP, the access to the northbridge is shared between the 
two. So each CPU would have only half CPU-Northbridge bandwidth as the single 
does.

(Intel seems fond of shared access to northbridge, and it happens on Itanium 
as well. It especially hurts them when comparing Xeon to Opteron, because the 
opteron scales up to 2 and 4 procs a hell of a lot better than Xeon. (Haven't 
seen 8-way #s) 

Opterons (and I believe Power derived, though I could be wrong) chips pretty 
much blow away conventional archs due to the re-location of the memory 
controller to the processor. 

In short, Intel's bus design sucks for scaling up in SMP due to 
northbridge-cpu design, and *if* that's the actual problem that's going on 
here, going dual xeon or pentium 3s won't help much, if they don't end up 
making it worse.  

James L

> --Joey
>