Quake strangeness

Bernd (bmeyer@cs.monash.edu.au)
Tue, 5 Nov 1996 11:48:31 +1100 (EST)

Hi there,

I got silly yesterday and _remotely_ started a copy of Quake on my
PC164, displaying on the Pentium. The two are connected with NE-2000
type cards (ISA in the ALPHA, PCI in the PC). I was fascinated to
find that in 320x200, I could still get 16fps out of it.....

Then, I got even sillier and started _another_ copy of Quake on the
ALPHA's local X-Server. And here the strange thing happened:

While the copy that had to send all its data to the Pentium reached
16fps, the local copy only reached about 6fps. According to top, they
both got equal CPU percentage; Also according to top (and vmstat), app.
half of the CPU-time was spent in system mode.

I can't seem to make sense of this --- why is the local copy so much
slower than the remote one? I tried running two local copies, and
they both get app. 20fps, which is as expected. I tried running two
local plus one remote copy, and the local ones became SLOOOOW again.

Is this a scheduler thing, where the remote Quake process gets scheduled
all the time due to network interrupts? But if so, why does top show all
copies getting equal CPU time?

I am thoroughly confused.....

Bernie

P.S.: Maybe it's a bus contention problem, with the PCI-ISA bridge having
higher priority than the PCI graphics card? Or could it be that there
is an ET6000 in the PC, but a Trio64 in the ALPHA?

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