Does it never work when you have the RAM in the other slots? Even when you are only using one stick? If so, I'd say update your BIOS, and if that doesn't work, get your motherboard replaced.
It works fine with 4GB (2 x 2GB) of RAM, even in the other slots. It just won't boot with all 4 slots (4 x 2GB) filled. I updated the motherboard to the latest BIOS v.1.2a, and reset all BIOS settings to default.
Motherboard supports 8 GB? Try running them at 667 MHz rather than 800 (might help).
When I install 2 pairs of DIMM's (8GB) on the X7SBL-LN2 motherboard the machine will not boot.
When I install ANY pair of these DIMM's in the blue slots (4GB) the machine boots OK.
I have the same mobo — and the same problem.
In a user review of this mobo (on newegg i guess) there's a hint that Supermicro made a newer BIOS for this board but they didn't make it publicly available, for unknown reasons. This newer version of BIOS allegedly solves the VT-d instability problem. So this guy emailed the support team about the problem he had and they sent him a link to a newer BIOS!
Well I live on the other side of the pond, and my English is a bit rusty.
So maybe you can email them (the address is listed here), explain the problem to them and request this newer BIOS?
I am using the C7P67 MB and the many types of RAM's out there don't always work for Supermicro MB, you have to review what they used and followed the same or get the fact sheet of the type of RAM's that do work and find one very close to the same. All the RAM should be the same type, don't mix, and watch the voltage, 1.8v only
I reviewed the Kingston versions and found one that works for mine, 16GB worth, #KHX1333C903B1K2/8G, took some time but works well.
BTW, what OS are you using
I am running Windows Server 2008 R2. I figured that this SuperMicro motherboard with 2 LAN connectors, a quad-core Intel Q8400 CPU (with VT-d), and 8GB of RAM would make an excellent platform to test Hyper-V.
All the Kingston RAM DIMM's are 1.8v and are identical, purchased from NewEgg at the same time.
The Kingston part # KVR800D2N6K2/4G is found on Kingston's compatibility list for this motherboard:
Perhaps this motherboard only supports 8GB of DDR2-667 RAM - not DDR2-800? Perhaps the Kingston web site is wrong - is this the most likely explanation? Is that why the Crucial web site only shows compatibility with 8GB of DDR2-667 RAM?
If you found a different speed on Crucial, then I would question what to use with Kingston, I would believe Crucial first.
Most of the time I use Crucial but I took a chance with the new MB using Kingston, the price was just to hard to let go for 16GB worth. Do watch the voltage called out along with Non-ecc or Ecc and channel type, SM is picky
Is the lower left portion of the MB unbalanced? At my last job we build a good number of 1U SM Chassis with X7SBL-LN2 and I found that the 1U heatsink bracket didn't fit in perfectly with the board. What happens was if I put in all the screws then it would just lightly bend enough that the leftward 2 RAM stick would either not show up, or cause other booting issue.
What I eventually did was only put in the 3 screws in the rear at the IO panel, and also used one of the plastic leg thingee that come with the chassis as support under where the SATA cables plug in. We also found that when a 1U case close, it could push the SATA cables down hard enough to also flex the board (thus also causing it to either not boot or not show up with all 4 sticks of RAM), and that's why we had to put a plastic leg support piece under that region of the MB to give it some support.
Once we figured out those trick, the MB setup work like a charm.
I have seen badly manf MB that were so warp after mounting in the case, things were twisted and connections failed, it happens.
Best thing to do with any new MB is to check the flatness before installing, cause a twisted MB when force to be flat can stress solder joints.
Reason why to worry with the heavy CPU heatsinks and MB's mounted vertical.
Also I check the RAM connector fingers to see if any are not shape correctly, could cause bad connection.
Then I look for cold solder joints, because sometimes during the initial setup for the wave solder machine the solder is not up to temp for the first group of MB's, things happen.