Athlon64 memory/FSB overclocking help needed

[8bit]

Hi all,

First, the specs:
Athlon64 3500+ Winchester
2x 512MB Kingmax Semiconductor PC4000 DDR RAM
Asus A8V Deluxe mobo (VIA K8T800 PRO)

Basically what I want to do is run the memory at 250MHz (effective 1GHz). In the BIOS I up the CPU core speed to 250MHz giving a memory speed of 1GHz. I drop the CPU multi from 11 to 9 to give a CPU speed of 2250MHz (should be fine with an Arctic Cooling HSF, right?). I go into the Hypertransport bit and take it down to 800MHz (which actually means an HTT multi of 4x the core clock of 250MHz) giving an effective HTT of the correct 1GHz again. I lock the PCI/AGP clocks at 33/66MHz.

The machine boots up fine, go into CPU-Z and see a CPU speed of 2250MHz, HTT of 1GHz, memory speed of 1GHz and PCI/AGP of 33/66MHz so all looks to have worked just fine. However when I run games the machine lasts about 5-10 mins and crashes.

So far I've left the voltages at stock and left the RAM timings on SPD. The RAM has heatspreaders so I don't imagine that's overheating. The CPU temp reports well within tolerances and it has an Arctic Cooling HSF anyway. Basically I want to know what I should tweak to get this CPU memory interface o/c stable, volts and/or RAM timings?

TIA
8bit

[Hottentot]

I would start by checking the actual memory timings against the recommended timings in CPU-Z. Then give the memory a little more voltage, followed by a session with the memtest program which will tell you if your memory is stable.
In fact it may be better to run memtest first anyway, beacause if your memory passes you will know the fault lies elsewhere.