Strange things after upgrading to 1GB of RAM..

I just added another 512mb stick of RAM to total 1GB of system memory. I decided to run Prime95 for awhile before running memtest because P95 is pretty memory intensive. Well when I booted up everything is running smooth, but after starting my P95 torture test everything is really slow. Like just to minimize my browser window takes a second or two. Now you would assume this would be somewhat normal b/c P95 is using all my CPU cycles and RAM. But when I had 512mb I would always run P95 and do other things in the background(browse web, ect), with nearly no noticable slowdown.

Why after upgrading to 1GB of RAM is my system slower when running P95 when theoretically it should be faster?

Is it a glitch with P95? Because I notice the same situation when I run it.

there is rumered that an older ver. of prime has a problem w/ 1gig of ram, but i think that they were having problems w/ it failing prime, but im not sure.....