I just recently purchased 8 gigs of ram and vista 64 to run it with. My problem is two fold: with more than 4 gb installed, the system will not boot into the bios. With just 4 gb installed, it will boot into bios but not my OS (although I can boot into safe mode with 4 gb). I have tried many combinations of ram voltages, clock speeds, and timings. I have also tried underclocking the FSB. I have tested all ram modules and ram slots, all are fine (the rig runs fine with 2 gb installed). Intel will not provide me support because my processor is not officially supported for this board. I have the latest bios and SP 1 for vista with all the latest updates (including the kb929777 update). If anyone has any suggestions, that would be great (do I not have enough power?).

OS: dual boot vista 64/xp pro 32
Mobo: Intel 975xbx rev 805
Ram: Kingston 2GB 240-Pin DDR2 SDRAM DDR2 667 (PC2 5300) 8x architecture
Processor: Intel e6750 1333 FSB
Video Card: Zotac 8800 GT 512mb
Power: RAIDMAX VOLCANO RX-630A 630W ATX12V V2.2
HD: 2 western digital raptors in raid 0 (xp boot), 1 western digital 300gb non-raid (vista 64 boot)

How many sticks total are you using?

It could also be your mobo doesn't support more than 4GB, i doubt it though...

They are 2 gb sticks, so ideally I would use 4, but it will not boot into OS with 2 sticks (4 gb ram). The motherboard is rated for 8 gb ram, but it's about 2 years old, so this may have been about the first generation that boards began supporting 8gb.

You might need to go in your BIOS and enable a "Memory Remapping" Feature. I remember that was an issue with older boards that supported up to 4GB ram...anything more than 3.2GB and they wouldn't boot or recognize anything higher. It might be the same with yours.

I've read some about people changing memory mapping or enabling memory hole's, but my bios doesn't have settings for any of those things (if I am wrong, please let me know). It's just the most up to date bios for the Intel 975XBX mobo. It's gonna suck if I blew money on vista and can't use all my ram.

Have you ran Memtest86+ on the memory to make sure there isn't a problem with any of the memory. Run it on one stick at a time then if they all pass try with two then four. Also some motherboards requirer a slight boost in memory voltage to use four.

Just one stick works fine. All individual sticks work (and all slots in the mobo work). With 4 gb (2 sticks) installed, I can get past the bios and can do the windows memory test at the boot selection screen. All sticks pass with 2 sticks installed. It seemed like the ram modules themselves were ok, so I hadn't run a memtest86+; I may try that later.

As said above, Try memtest with each stick. For sure try 2 sticks since thats what does not make it to windows.

4 sticks is harder on the chipset then 2 so you may need a bit of chipset voltage as well.

I have a x975 board and can say that Intel took away official support for 1333 for a reason. Not all X975s will run properly with 1333. I have one that will not run ANY 1333 fsb cpu.

When you say you tried lower the fsb, did you go as low as 1066? and the memory as low as 533(that is 1:1) just for testing?

Do you have all the latest updates for windows(may at least help 4gigs work)?

I 've tried using 2.1 and 2.2 voltage settings. The comp runs great with the 1333 proc and 2 gigs of ram...had it this way for about a year and it's very stable. I didn't underclock it that low...that's a 20% underclock right? (This bios changes the FSB clock speed by percentage). I've had the ram down to 533 but haven't matched it with the fsb. I have SP 1 for vista and all current updates.

Have you heard of any specific info about the 1333 proc and ram usage?

Ok, It boots with 4gigs. Try to boot that way to run memtest to check for errors.

Can you please link to your exact memory. What is its MAX voltage.

This site will give you a bootable ISO image(CD) you can use to test memory independent of windows. Let it do a few passes or better yet overnight.
http://www.memtest.org/#downiso

It boots into the bios, or safe mode for windows xp/vista64, but does not boot in to actual xp or vista64 with 2 sticks (4 gb) installed. Bios will not boot with greater than 2 sticks (4 gb) installed. A single stick will work with any voltage setting (1.7-2.2), but it looks like the schematics specifiy 1.7, 1.8, or 1.9:

http://www.valueram.com/datasheets/KVR667D2N5_2G.pdf

I performed memtest with two single sticks (one at a time) in two separate slots, with no errors. However, when I used two sticks together, both which had no errors by themselves in the tested slots, I received multple errors beginning around test 6, and eventually the test would stop, unable to complete the first pass. I assume this means the ram is good, the slots are good, but the chipset is having some problem handling the ram.

When I test 2 1 gb sticks (different ram altogether) running in dual mode, I have no problems.

I'm thinking that when intel advertised this board as supporting 8 gb ram, it meant under very narrow and specific conditions.

Also, I thought about your comment regarding the lack of support of conroe 1333 on 975x boards. Although I know that no official support is offered, I think anything over the 804 revision is supposed to have fixed that.

I appreciate all the comments so far from people trying to help!

Sometimes looking at the QVL for the board will give you a better idea what memory will work. It's quite common for boards to require single-sided RAM only when all the slots are filled.

From the link below, intel indicates that the only 2 gig modules supported by the board are double sided configurations. As 4 gig modules are not listed as being supported, and the board is specified to support 8 gig ram, I can only assume their intended method to get 8 gigs of ram on board would be 4 double sided 2 gig modules.

http://www.intel.com/support/mothe [...] 026567.htm