I run redhat 8, on p3 450, with 128 mb ram & 256 mb swap.. i find that when i am running xmms and try even scrolling the windows.. the music gets paused for a sec.. even minimizing does this... i tried investigating to find that x server consumes an avg of 12 % of cpu power.. ! isnt that drastic..? i have a s3 trio 3d/2x 8 mb video card. its vesa compliant.. is there any workaround for this problem

12% isn't so drasctic if you are running XServer with Kde, xmms, few application running while surfing on internet...
And your video card isn't powerful, so your cpu probably have to make few more calcul.

But still, my xmms player still playing even if my cpu hits 99% of use.
You might have some other troubles. Take a look if you have enabled DMA for your hard drive (type man hdparm). Also make sure you don't have a lot of useless application running (RedHat is annoying with the very heavy "updatedb" starting every boot as example)

If you want to "see" what is the application consuming your cpu, try "top" and then type "P".

I've had bad experiences with S3 cards. They don't seem to pull their weight when it comes to 3D effects, or even 2D effects. It sounds as though your processor is trying to make up for the rendering your video card isn't processing fast enough to keep X happy.
I'd suggest turning down some of the fun X effects. For instance if you're using KDE, go into the Control Center and open Look&Feel->Style and select the "Effects" tab and either disable all or some of the effects to try to keep the load on your video card at a minimum.
Also you can try not using a large picture for a desktop background or even not using a picture at all (if you are anyway).

Just a suggestion,

SIR_Taco