Help please with new system

I recently bought a hp dx2250 for a bargain price of £185.00 after the £50.00 cashback from HP. This to replace my ageing agp Shuttle xpc sng5v3

AMD Athlon X2 5000+ Processor
2GB Memory
250GB Hard drive
DVD-RW Optical Drive
Gigabit Ethernet
Vista Home Basic Operating System

The standard power supply is lite on 250w.

I decided to buy a pcie HIS Radeon 3850 HD, i had read they were low on power consumption. Fitted fine but i wasn't a little dissapointed in benchmark results in 3dmark06 etc.

I ran the call of duty 4 demo fine looked great no crashes.

I installed amd power monitor and noticed the core frequencies fluctuate betweem 1000mhz and 2400mhz, the voltage does too between 1.1v and 1.5v.

Following on i installed CPU-Z and again the core speed, multiplexer and bus speed fluctuate rapidly.

Is this normal behaviour or is it a sign that the power supply is struggling ? I did use the online power supply calculator and based on the hardware 1dvdrw, 1hd, cpu, video card it should be sufficent.

Is there a good game demo to show fps and expected fps based on the graphics card being used ?


Thanks in advance

http://www.tomshardware.com/forum/ [...] multiplier

Although it's directed to C2D, you can pretty much get the basic idea.