System problem - Motherboard or RAM?

[coolnm]

I had built my own system a little over a year back. It was working fine until recently the machine started showing BSODs with different error messages everytime. I am running Visa Business 32-bit on it. (using only 3GB of the available 4GB RAM). One restart Vista indicated a couple of times that the HDD has some problem so I ran WD diagnostics but that came out clean.
I have 4 RAM DIMMS.
I removed 3 and using Windows Memory Diagnostics tested just 1 DIMM installed in Slot 1. The advanced tests (run over at least 8 hrs each) passed with 3 DIMMs and failed with 1. Now I started the PC with only 2 DIMMs installed in dual channel mode. Vista BSOD crashed. Windows memory diag failed. Now again I tested the 3 DIMMs one by one and they failed the memory diagnostics. Sometimes some DIMM used to pass the test.
So now I installed one DIMM in slot 1 and set the RAM settings from BIOS manually. I did set
Memory voltage : 1.90V
DDR2 SDRAM Clock Manually set to 800MHz
SDRAM CAS Latency: 5T,
SDRAM RAS to CAS Delay (tRCD): 5T
SDRAM Row Precharge (tRP): 5T
SDRAM Active to Precharge Delay (tRAS): 18T
Command Rate: 2T

The memory diagnostic still failed. I know I haven't used memtest but by now having spend days and hours on the problem I am too frustrated to try on a new diagnostic utility. If someone highly recommends using memtest then I will give it a try.
At this point I am leaning towards the assumption that the motherboard has gone bad. Any thoughts to further troubleshoot the problem?
Also if I were to get a new motherboard what would be a recommended one (I dont want to spend a lot). What other components would/should I upgrade to make the system stable? I am leaning towards Gigabyte GA-EP45-UD3P or the cheaper Gigabyte GA-EP45-UD3LR.

Current System spec:

1 x Pioneer 20X DVD±RW IDE
1 x D-Link Wireless-G 54Mbps PCI adapter
1 x Western Digital Cavier Green 500GB
1 x Antec Sonata III Mid Tower Case with 500 Watt PSU
1 x BFG GeForce 8800GT OC 512MB Video card
1 x Corsair TWIN2X2048 2GB Kit (2x1GB) DDR2 800MHz/PC2-6400 XMS2 Memory 1.90V (5-5-5-18)
1 x Corsair TWIN2X2048 2GB Kit (2x1GB) DDR2 800MHz/PC2-6400 XMS2 Memory 1.90V (5-5-5-12)
1 x Intel Core 2 Duo E8500 3.16 GHz Socket 775 1333MHz 6MB L2 Cache with heat sink
1 x MSI P6N Diamond Motherboard

Yes, I realize tRAS is different .. its 12 for 2 DIMMs and 18 for the other two. I had brought the second pair later and that time I tried to get the second pair as close in settings to the first but couldnt get the exact same thing.
Until now the PC was running fine with all the four DIMMs.

I have been testing with 1 DIMM at a time in slot 1 (I also tried slot 3 separately) and that is also now failing both with automatic BIOS RAM settings as well as manual except for one of 5-5-5-12 DIMM in manual setting.

Earlier when I found that the memory diag was not failing for one 5-5-5-18 DIMM, I tried to start the PC on that only one DIMM. Vista crashed couple of times before finally loading and some time later it again crashed with a BSOD. So I again ran the memory diag on the same DIMM and this time it failed. :frown:
This inconsistent behavior is frustrating.

 

[mpilchfamily]

You should run Memtest. You may also want to try upping the RAM voltage up to about 2.0V or 2.1V. It may be that the RAM isn't getting enough power from the motherboard thus causing the problems.

 

[Zensal]

Sorry, I agree with the above post. Memtest is a better program for checking the memory.

But that said, I kind of agree with you about the mobo. Is there another computer you can check the RAM in?

Edit: If you do find that it is the mobo, then FYI, I'm running a UD3R and it is a great board. Only get the UD3P if you need/want the dual x16 slots.

 

[coolnm]

I tried memtest86+-2.11 .. ran at least 7 passes
With only one 5-5-5-18 DIMM in slot1 the test passed. With only the other DIMM in slot 1, the test passed.
With both DIMMS in dual channel mode i.e. one in slot1 and other in slot3, the test failed.
I tried the above stuff with RAM voltage set to 2.0
I didn't try the other pair of DIMMs.
I have given all the DIMMs to a friend for testing.