Need help to install 8GB of memory for ABIT IP35 PRO

I looked for several days through alot of websites to figure out my issue.

I want to get 8GB of RAM on my pc. Here 's the detail:

WIN XP 64bit SP2
Intel 2 Quad Q6600
BIO Version 6.00 PG Date 5/26/2008
2 x 2GB PATRIOT PC2-6400 4-4-4-12 @2.1V
2 x 2GB OCZ PC2-6400 800Mhz 4-4-4-15 1T @2.1V

I got C1 Beep Code whenever I tried to install the sticks of both types together. The boot does not pass the POST screen and give a single BEEP code repeatedly. I tested and all of the sticks worked separately fine for each type as well as the slots on motherboard.

I cannot do mix and match or go over 4GB. I tried to set up the voltages but I had not found any luck.

I am wondering can it be the issue of different manufacturer of RAM? Any idea or help is really appreciated.

Yep they're probably wanting different timings. Did you try swapping them around? I know that 4x2GBs of matched sticks work okay on that board. Poke around for different BIOS revisions with better dram support.

If the timings for the 2 sets are significantly different, you might try manually setting them in BIOS for the looser timings between the two sets. Ram will always run looser Also make sure to supply enough voltage for the hungriest set. If that doesn't work by itself, a different BIOS like TimoneX suggested will be your best bet.