HANDS ON GUIDE

Step 3: Memory troubleshooting

Problem number two is memory. As we mentioned earlier, memory speed is directly related to FSB speed, so when you raise the FSB, you're also increasing the speed at which your memory runs. If your memory can't handle this speed, problems will occur. I built my test PC with 2GB of Kingston HyperX PC2-6400 memory, which is rated to run at 800MHz. At its default settings, the Asus board configures the RAM to 'Auto', which, in the case of our RAM, meant that it was already running asynchronously at 400MHz (800MHz effective due to 'double data rate') when the FSB was set to 266MHz (a ratio of 2:3). However, by raising the FSB to 300MHz, the memory speed also increased and was now running at 450MHz, which equates to 900MHz effective - 100MHz faster than its rated speed.

This could be the cause of the problem, so to remove memory speed from the equation, I manually set the DRAM frequency to it's lowest value using a 1:1 divider, which reduced the memory speed to 600MHz with an FSB of 300MHz.

It's also worth noting that the BIOS doesn't always do a great job of reading the SPD (a chip that stores frequency and latency settings) on the RAM modules, and if you have low-latency memory, it's possible that the BIOS will have set more conservative values than those of which the modules are capable. I Googled the part-code of my memory and found that it can run at 4-4-4-12 timings at up to 800MHz, with 2.0V. I manually set these timings and the voltage value in the BIOS.

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