MKV playback strangeness...

[mh2360]

I have two PC systems, one is a simple Sempron 2400+ (1.67ghz) 768mb RAM with a GF6200A, and the other is an Athlon XP 2800+ (2.08ghz), 1GB RAM with a GF6200A.

I want to play back MKV files at 720p, so I obviously need to use the faster of the two systems as a HTPC, the problem is, even though the Athlon PC is a minimal Windows Media Edition 2005 setup with nothing except codecs and drivers installed, I experience jerky playback with 720p MKV files.

The slower Sempron system on the other hand gives me smooth 720p playback with no problems, even though the system (XP Pro SP3) is bogged down with every crap bit of freeware you can imagine, and has 256mb less memory..

Both have identical drivers, codecs and settings (where possible), the only other major difference between the two systems is the motherboard (even the brand of memory is the same).

Can the make and model of motherboard have such a drastic effect on a system's performance?

[Baldrick]

Have you checked the task manager cpu perfomance tab? Does it reach 100%? and no other software are stealing cpu?

I doubt that the motherboard will make that much difference.

[mh2360]

There isn't anything stealing cpu time, there's nothing else installed on the XP MCE system, only needed codecs and the latest updates.

I thought at first it might be SP3, but both systems have it now, and the slower CPU still performs better.

I'm beginning to think that it might be Windows Media Center itself that is causing the trouble, the problem seems to be getting worse as my media library grows. (?)

It gets even more confusing when I monitor Windows Media Player in the Task manager on both machines playing the exact same file. On the slower CPU the usage averages at around 70, on the Athlon XP it is around 90+.

Something is causing WMP to use more CPU time on the Athlon XP system. (there are no plugins installed FWIW).