dual channel

[JcT21]

hey all ...anyone have experience using dual channel mobo/ram?

i have athlon 64 3800 2.41ghz
vista hpe
2gb pc3200 running as dual channel 400

now, i have extra sticks of ram, but different sizes. i install a 512mb pc3200 and a 256mb pc3200 and the dual channel goes to single channel 333 even though all 4 sticks are pc 3200.

now, if i use the same memory size, say either 2 x 512 or 2 x 256 ..along side the already installed 2 x 1gb sticks, will it sitll be dual channel 400?

however the 2gb dual channel scores a 5.0 on vista, while the 2.7gb scores a 3.8 running as single channel 333.


sooo... if i purchase either a 512 or a 256 stick and use it in addition to my 2gb dual cahnnel, will using all 4 sticks still run at dual channel even though slots 2 and 4 will have different sizes (but the same speed). ????

[Pinion413]

The best way to go is to use actual dual-channel kits as they are paired for each other.

From what I understand, you can run a 3GB (2x1GB and 2x512MB) or 2.5GB (2x1GB and 2x256MB) so long as the appropriate pairs are on the appropriate channels.

It would be best if you were looking to find another stick of either 256 or 512 that it be as close as you can possibly get to the specs (latency timings, etc.) of the stick you're looking to pair it to in order to avoid compatibility issues.

[JcT21]

what i have is 4 ram slots ... in slots 1 and 3 i have 2 x1gb pc3200 sticks, same speed, same brand ... and i have laying around 1) 512 pc3200 and 1) 256mb pc3200


when i add those extra sticks in slots 2 and 4, my speed drops to single channel 333 instead of the ddr 400 speed that the 2gb runs at alone. so i was wondering if bought either a 512 or 256 that matches what i got already, to run in slots 2 and 4, along with the 2gb i have in slots 1 and 3, would it still run at dual channel 400 or would it just be all messed up.. :-)

so what i would end up with is a gig of ram in slot 1, gig is slot 2, and either 512 or 256 in slots 2 and 4. ....in order for dual channel to work properly would slots 2 and 4 need a gig of ram?

sorry i sound confusing when i try to explain this its like im typing in circles lol
but thanks for all ur guys help, it is appreciated!!

[Pinion413]

It's alright.

On a separate note, your motherboard knocking it down to 333MHz from 400MHz when you have all 4 installed (assuming they're all PC3200) may be due to compatibility/stability issues. The ASUS board I have in this rig (nForce 4 SLI chipset) will limit the RAM to 333MHz when all 4 slots are used if all the RAM does not match each other. It can manually be bypassed in the BIOS by entering my own settings. That could be your 333MHz limiting problem.

As for Dual Channel, both pairs need to be of the same size and type. You can have 2x1GB running with 2x512MB or with 2x256MB, but not 2x1GB with 1x512MB and 1x256MB. Though if they are all PC3200, they should run in DDR400, but due to the odd pairing of one of the sets, it will not run in Dual Channel mode.

So long as both of your "pairs" of memory slots both support Dual Channel on your motherboard, you should be able to run 2 sets (of 2) in Dual Channel at DDR 400.

Most baords that I have dealt with pair off for Dual Channel on the odd and even number slots (so I am assuming that in my description). Since you currently have 1GB each in Bank 0 and Bank 2, they run in Dual Channel for you.

You should be able to run 2x512MB or 2x256MB (one or the other) in Bank 1 and Bank 3 and maintain Dual Channel capability, provided the memory is of the same type and size as the one stick you're trying to pair it with (though preferably getting another Dual-Channel kit eliminates this concern). You can't put 512MB in Bank 1 and 256MB in Bank 3 and maintain Dual-Channel.

So, if you were looking for a recommendation, so long as your board supports Dual Channel across all 4 of its memory slots, I would obtain another stick of either 256MB or 512MB that is of the same type as the one you currently have that you'd like to pair it with. If that is going to be difficult, then get your hands on a 1GB (2x512MB) PC3200 Dual Channel kit.

Hopefully that made sense and helped. :grin: It is getting late and my head's a little foggy. :zzz:

[CoriBright]

It's an AMD Athlon CPU... it generally will not support 2 pairs of dual channel at DDR400, it will automatically 'downgrade' them to the lower speed. Why? AMD are unable to tell anyone the answer to that, even though many of us have asked.

It may be some BIOS issue, but if so, no one is able to write a BIOS that fixes the issue.

However it doesn't matter if all the RAM is exactly the same or not the same. You just have to live with it or change motherboards to one with DDR2.

[Pinion413]

It's an AMD Athlon CPU... it generally will not support 2 pairs of dual channel at DDR400, it will automatically 'downgrade' them to the lower speed. Why? AMD are unable to tell anyone the answer to that, even though many of us have asked.

It may be some BIOS issue, but if so, no one is able to write a BIOS that fixes the issue.

However it doesn't matter if all the RAM is exactly the same or not the same. You just have to live with it or change motherboards to one with DDR2.

I encountered that on this rig when I first built it. At the time, I was running an Athlon 64 3500+ with 2 sets of Dual Channel PC3200 (2x512 and 2x256). The board would default the RAM (with all 4 slots occupied) to 333MHz for "compatibility reasons" (even listed as such on ASUS's support site with the solution), but it was easily corrected by setting the RAM manually in the BIOS. I have since upgraded to an Opteron 180 and 2x1GB of Dual Channel, so I just let the BIOS handle the RAM automatically again.

I was always under the impression though that it was an nForce issue, that it became unstable with certain RAM (quality and manufacturer) combinations, not an AMD issue.....

I reserve the right to be wrong..... :lol: