Ques. on dual-channel memory

[JWMiddleton]

In a recent article on the Sempron 3100+ THG stated "...and you should to have a matched pair of DIMMs too."

I have an ASUS A7N8X Deluxe board with AMD XP 2500+ CPU dedicated to crunching SETI. I had a matched pair of Corsaid DDR400 modules installed and the system crunched like crazy. I got a new P4-3.2GHz mobo combo from Fry's and wanted to move the 1 GB of RAM to it. So, I got a pair of DDR400 256 MB modules with Micron chips of a For Sale/Trade Forum. They do not have the same timing as the Corsair modules, but since the CPU is only running at 333 FSB, I figured they would handle tighter timing. Well, with the original chips I was getting 9 work units a day with times of about 2H 25M, but with the new RAM the times are over 3h. It does not appear that the new modules are running in dual channel mode.

Is there something special about modules to allow them to work in Dual-Channel mode? Is there a way to force the mobo to run them in that mode? Any help will be appreciated. This is not a BIG deal, but one that I am curious about.

 

[Crashman]

Dual Channel mode is enabled on Intel chipsets when you mount a pair in slots 1 and 3, or 2 and 4, or two pair in that order (1-3, 2-4)

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[JWMiddleton]

Thanks guys! When I went in and moved the memory I found that the FSB was set to 133. When I changed the memory earlier that happened and I had not noticed it. I reset it to 166 in the BOIS and the system would boot and then after only a few mins...or maybe not a full minute, it would reboot. I reduced the FSB to 150 and it was fine. I let it run a few days and bumpted it to 159. It is still running fine. I checked the memory settings and they are at SPD. I verified that with CPU-ID. So, I dont't know what is going on with this system. I do have the memory running in dual channel mode, but with the reduced FSB I am stil not crunching as fast as I was originally, but it is a great improvement over last week.

 

[Crashman]

Since Socket A doesn't need the extra bandwidth, it would be better to have the thing run in single-channel mode rather than underclocked. Try single-channel mode, and if that makes it stable at the proper speed, you'll be better off.

It sounds like your RAM simply isn't stable at full rated timings in dual-channel mode. There are other ways around the problem, such as raising RAM voltage (vDIMM) or using slower timings.

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