[mythtv-users] Squeezing more performance out of my system

[Piers Kittel]

Hello all,

One of my frontends - I used to have a completely diskless P3 666MHz 
133MHz FSB processor with 256MB PC133 RAM along with a Geforce MX4000 
and an Intel network card but had problems with it powering itself off. 
  So I upgraded to an AMD Athlon Thunderbird 800MHz processor with 
100MHz FSB along with a PC Chips motherboard with a SiS chipset and 
onboard LAN/audio but the other hardware (RAM/video card/etc) is exactly 
the same.  No more powering itself off problems.  I found the P3 666MHz 
to be perfectly smooth - not a single jerk at all, while I find with the 
Athlon to have very slight jerks every second or two - random, can't see 
a pattern (tho might be related to subtitles changing to the next 
subtitle but only occasionally).

The backend is a dual DVB tuner system recording PAL SDTV.

The kernel is 2.6.15 compiled myself with as much drivers removed as 
possible - using the same .config file as the kernel I created for the 
P3 666MHz but changing the CPU type and drivers for the chipset etc.  Am 
using nVidia's lateset drivers etc.  Not using pre-empting though I think.

Still can't get rid of very annoying but very slight jerks.  Load 
averages seems OK - about 1 to 1.5 and CPU usage is about 60 percent 
when playing back a recording.  RAM usage is usually 240MB used out of 
256 where 90MB is cached (wonder where all the RAM is going! :))

DVD discs plays back perfectly fine.

Tried the following:

Mount the backend's /video onto the frontend
Underclocking the memory bus speed to match the processor bus speed 
(i.e. from 133MHz to 100MHz)

Slight improvement each time.  Is there anything else I can do to 
squeeze more performance out of the computer system to stop this 
jerking?  I'm rather surprised that upgrading to a faster AMD Athlon 
from a P3 would mean a decrease in performance, or is it down to a poor 
quality chipset/onboard LAN?

I did think it was due to netbooting/NFS/networking overheads etc but 
the old P3 666 was fine.  Is it possible that going down to 100MHz FSB 
made the problem happen?

Thanks to everyone for all your help.

Cheers - Piers