I picked up more RAM today and it's not playing nice with my existing RAM. I can't get all 4GB running at 800 MHz (400 MHz in dual channel). Yes, I know about the Windows limitation on capacity, but I'm not really worried about that unless it's related to my speed issue...

I have an Asus M2N-SLI Deluxe with 2GB (2 x 1GB) of Corsair XMS2400 PC2-6400 and I added 2GB (2 x 1GB) of Crucial Ballistix 128MX64DDR2 PC2-6400. Problem is the memory is running at 368.4 MHz in dual channel instead of 400 MHz.

I've uploaded CPU-Z screenshots of all the memory timings:

CPU-Z Screenshots

The two Corsair sticks are slots 1 and 2 and the two Crucial sticks are slots 3 and 4 which is the correct setup for dual channel on identical pairs.

Can anyone help me set my BIOS timings to get everything running at 800 MHz (400 MHz dual channel)? I know I need to specify timings in BIOS but I can't figure it out and the variations I've tried have all resulted in 368.4 MHz.

BIOS has a TON of options to set but I think I'm interested in the following:

Tcl
Trcd
Trp
Tras
1T / 2T Memory Timing

But there are plenty of other things to choose from and I have no idea what they are.

Any help is greatly appreciated!

Recommend searching the ASUS forum and posting there if you haven't already. Good luck.

qcumber98 said:Recommend searching the ASUS forum and posting there if you haven't already. Good luck.Good suggestion - I did just now.

However, I'm more optimistic that I'll find help here as I don't believe this is a problem with the motherboard but simply a question of what timings I need to set that are compatible with both sets of memory at 400MHz...

I'd used the JEDEC SPD timings for the slowest memory module in the system, and sometimes slowing some of the settings will cause a higher memory bus speed to be reported. However it's common for the bus speed to be reported as being slower when more than one module is installed, and maybe the BIOS does this as a precaution because more modules mean more loading of each signal line, and that can mean the signals turn on and off more slowly. A slower bus speed does not mean there are bad bits.

qcumber98 said:Well, from what I've read online, it's a limitation of the memory controller in your CPU and the M2N-SLI Deluxe is not good at overclocking. If it's possible to run at full speed, ASUS should do the right thing and let their users know how to do it. Otherwise, it's a raw deal to have to run PC2-6400 at DDR2-667 speed.Thanks for the feedback. For what it's worth, the Corsair memory was running fine at 800MHz before I put the Crucial in. That's why I assumed it was an incompatibility in the timings between the two brands...