Windows 7 - Windows won't boot with 8gb ever since Radeon 6950 was installed

Hi, I got a problem with my ram ever since I installed my new Radeon 6950 card. I can only use 6gb of ram (1 in slot 1, 1 in slot 3 and 1 in slot 4) I can't seem to have all four sticks in at once, and I don't think it's actually the slot itself malfunctioning. Also, the ram is all the same, and worked perfect before the new GFX card, and they are all functioning properly.

This happened instantly after I installed my new card, and hasn't worked since. I have 600w power supply so I don't think it has anything to do with the power supply.

I need some serious help here, because I've been up and down forums all over the internet and can't find a fix. Any help appreciated, thanks.

is there any configuration in which ram does work in slot 2 right now?

No, last I checked this was the only way I could get it to work, I know it sounds like a damaged slot, but I really don't think it is. Is there a good way to test that?

Yes, put 1 stick in slot and try booting.

Right...lol. I'll do that when I get the chance and get back to you asap, thanks.

It could also be a result of a need to update the bios.
You may want to look into that as well
(assuming the above suggestion works)

Yeah, I think I did that a while back when I first got the problem, I suppose I should try again, what's the best way to do that?

If you still have the old video card you can test the (bad?) slot by reinstalling the card and all the RAM. If all four sticks work with the old card then you can reasonably assume the slot is good.

But it certainly sounds like a power issue. There are many kinds of power issues.

It would help greatly if we knew:

• Brand and model number of old card and new card.
• Brand and model number of the power supply
• Brand of the BIOS (AMI or Award or Phoenix).

It could be that you just need to increase the voltage to the RAM slots to overcome a motherboard shortfall.
It could also be that the power supply is defective and is cutting out on increased demand.

Tests will be needed to determine which.

Okay, so I've determined that slot 2 probably doesn't work, since I put 1 stick in it by itself and my computer doesn't even boot. Here are my specs:

Windows 7 Home Premium 64 bit
Gigabyte Motherboard P55A-UD3P
600w power supply, not sure of the make.
My video card is a radeon 6950

Now I'm just looking at my system info and it says total installed memory: 6GB, physical memory: 4GB, available memory: 2.36GB. So I'm guessing that I'm just running with 4GB of ram, rather than 6GB. Is that because the ram must be paired to work properly?

No, the RAM will 'work properly' regardless of the configuration. If you install 1GB of RAM in one slot the system will recognize and use 1GB of RAM in Single Channel Mode. If you add another 1GB stick the system will recognize and use 2GB of RAM in Dual Channel Mode. If you add a 3rd 1GB stick the system will recognize and use 3GB of RAM in Single Channel Mode.

Single channel mode uses all of the installed memory using the normal system bus bandwidth. Dual channel mode simple doubles the bandwidth. It does not affect the amount of memory installed, reported, or used.

Your motherboard manual recommends

"If only one DDR3 memory module is installed, it is recommended to install it in the DDR3_1 or DDR3_3 sockets."

That means the system may not boot with only one stick installed in Slot DDR3_2 by design. You can test this by populating DDR3_1, DDR3_3, and then DDR3_2.