So I got some more RAM for my computer...my motherboard is supposed to support up to 3GB in 3 DDR slots. It supports dual channel at speeds up to PC3200/DDR400. I'm running an AMD Athlon XP 3000+, 333MHz FSB.

I've been running one double sided 512MB DIMM module until now, when I got two more 512MB DIMM modules - but they're single sided. Same brand, same size, same speed. I checked the manual and it says mixing single sided w/ double sided is perfectly fine...

Anyway, with all three inserted (the single sided ones in slots 1, 3; which correspond to channels A and B for dual channel operation, and the double sided in slot 2) its running dual channel but for some reason is only recognizing 1GB of RAM instead of the full 1.5GB that is installed.

I dont know if any of you are computer savvy...I just thought I'd take a shot.

Wow! Never heard of that kind of an ECU upgrade!!! :rolleyes I've gotten so behind the curve on PC's, it's sad! Good Luck!

What brand and model# is your mobo?

its a Gigabyte GA7N400S-L.

Manufacturers Site (http://www.giga-byte.com/MotherBoard/Products/Products_GA-7N400S-L.htm)

Based on nVIDIA chipset specification, the motherboard you have only support 3 DIMM slots officially. When a MB comes with GIGABYTE unique memory H/W deisgn, the board you have can provide the extra DIMM slot and make users get better flexibility on H/W installation/expansion. But, because the quality of memory modules in retail market is uneven, thus, when you install 4xDDR400 memory modules on the motherboard, our MB BIOS will decrease memory speed to make sure most system will bootup properly.

I know the above isn't exactly what you're running, but could the fact that since 2 DIMMS are single-sided, and 1 is double-sided, the BIOS is ignoring the double-sided one for stability purposes? Not 100% sure, but just thinking out loud...

well I'm gonna see if I can find someone thats got a single sided PC3200 DIMM module I can borrow and see if that works...and maybe later I'll start switching the slots around and seeing what happens.

I ended up taking the DS one out, because when I started my computer it would only load windows about half the time...it would POST and everything but when it came time for the windows loading screen the screen would go black and just sit there.

yeah, it's usually never a good idea to mix n' match RAM. I only put identical sticks in there, just saves a lot of future headaches.

well my original plan wasn't to mix and match 'cause I know that often causes problems...I swear I thought it said double sided on the two new sticks I ordered from newegg.com, and they were the same brand and speed as the one I had...but they got here and were single sided.

I may order one more single sided stick and sell my double sided one to my roommate or something, he's building a computer with an AMD Athlon XP 3200+ with 400MHz FSB but the RAM he has is only PC2700/DDR333.

Before I order another stick, is there any other reason this might be happening that could still cause the same issue when all the RAM is identical?

The issue has nothing to do with your dual sided vs. single sided memory.

If you want to run dual-channel memory, you need multiples of 2 sticks. You can't run dual channel and single channel at the same time on one motherboard, so it's ignoring the third stick because it cannot function in dual channel mode without a mate alongside it. You might be able to turn off dual channel mode entirely in the BIOS and just run all three sticks in single channel mode, but dual channel will greatly improve performance if you leave it on. So you really ought to ditch the one stick that doesn't match the others or buy another one to run alongside it.

ok well I just discovered something new...

I was trying different combinations, first I put just one SS in channel A (DDR1) and the DS in channel B (DDR3) and it worked.

Then I put the other SS in DDR 2 and it wouldn't POST.

So then I took the DS out of DDR3 so I had both SS sticks in DDR1 and 2 (both channel A). It froze during the windows 2000 loading screen.

So you're right that the SS/DS is irrelevant...and it makes sense that it wouldn't run in dual and single channel simultaneously, which sucks since I only have 3 slots...but I'm thinking now that theres something else in my system thats causing problems with the DDR2 slot.