I have a AMD 3800+ x2 on a Skt AM2.I have recently bought 2GB of Ballistix Pc2-5300 (667mhz).Turns out that you need a processor that will run at at least 250 FSB for these modules to run at their default 667mhz,so at mo their running at 533mhz with processor clocking at default 2.01Ghz.

Now i can overclock this processor to 2.6Ghz (Very stable),which is above 250 FSB that is needed to run these Ballistix at their default 667mhz,only trouble is,i have to lower the memory speed down lower than 533mhz to achieve this.
I not very good with the memory timings etc,is there a way these modules can run at their top speed with what i have,or am i looking at maybe buying the 5000+ AMD dual core which i know clocks 2.5Ghz default.

A64s, X2s, & Opterons have no FSB. The CPU communicates with the memory controller at full processor speed, which in the case of your X2 3800+ is 2000MHz. The memory controller & RAM then communicate with each other at the default speed of the RAM (or whatever you've manually set it to run at). And the CPU communicates with the board on a Hypertransport bus which runs at 1000MHz (DDR2000).

Your DDR2-667 RAM runs at 333MHz by default. There currently are no A64s, X2s, or Opty's that have a CPU freq higher than 200MHz. In short, there are no AMD CPUs that operate at 250MHz 'FSB' by default. As for the 5000+ CPU that you mentioned...it runs at 2.6GHz, not 2.5GHz, & the default clock setting is 13 x 200MHz.

What you said about changing the RAM freq when you overclock is 100% correct. When increasing the CPU freq from 200MHz to 250MHz, you have to lower the RAM freq setting from 333MHz (DDR667) to 266MHz (DDR533)...the RAM then 'overclocks' along with the CPU & the speed jumps from the manual setting of DDR533 back up to DDR667 again.

I see no problem with what you're doing...as I said, you've overclocked exactly how you should have.