Problems with TWIN2X2048-8500C5D and Gigabyte p35-dq6

I am getting random lock-ups and BSODs.

 

Processor: Core 2 Quad Q6600 LGA 775

Memory: 4gb of TWIN2X2048-8500C5D

Motherboard: Gigabyte P35-DQ6

Video: GeForce 8800GTS; 640 MB

OS: Vista Home Premium

 

I have been grappling with issues ever since I put this machine together back in August. First, I determined one of the slots on the motherboard to be defective by testing each memory module in each slot, so I RMAed the board. Before I returned it, my system was running flawlessly on 3gb for about a week. Ever since I got the replacement and put everything back together, i've been getting lockups and blue screens mostly when playing games; however it seems to be limited to certain games. I've crashed several times in one hour while playing World of Warcraft, ive crashed twice while watching a movie, yet only on that one occasion. I've also played about 20+ hours of team fortress II with not one crash. Memtestx86 initially found errors in test 5; after running for about an hour or 2 it found no errors other than ones in test 5. I noted a FAIL for DDR18V in my bios, which was a common problem with this model of MB, and that was fixed by upgrading my bios to latest revision. After that, test 5 no longer found any errors. I didn't re-run the other tests, though.

 

I've still been getting the crashes, sometimes more frequently than not. Also, when I left my computer idling while going away over night, I found that it had crashed and rebooted when I got home the following evening, so I ran memtestx86 again. Now I immediately get lots of errors on every test. What are the proper timings for this memory? I currently have them running at 5-5-5-18, I know they are supposed to be set at 2T but I don't know which option that is. Additional memory settings include:

 

Memory frequency: 1066

tRRD: 3 [AUTO]

Rank write to READ delay: 3 [AUTO]

Write to precharge delay: 6 [AUTO]

Refresh to ACT delay: 42 [0]

Read to Precharge delay: 3 [AUTO]

tRD 4 [AUTO]

tRD Phase Adj 0 [AUTO]

Try setting the memory frequency to 800 and see if that does anything. You sound like you went the route I did with a different vendor's memory. 4 1GB sticks that should do 1066. But after a month of stability, I started getting BSODs and crashes. Had to step down to 800 (and different timings) to get stability back. Prime95 wouldn't last more than five minutes and MemTest86+ failed in test #5. After dropping to 800, both MemTest86+ and Prime95 run for hours.

The memory controller can not keep up with the extra DRAM at the rated 8500 speed. It's taken some time to show up but you will need to drop the speed of the DRAM from 1066Mhz to 800Mhz. If you had purchased 4 X 1024MB of PC6400 (800Mhz) DRAM, then you would have had to drop to PC5300 (667MHz) DRAM, etc. 2 X 2048 will not issue this problem. This is a problem of all 4 banks being populated.

 

Think of it this way. If you have a small phone book, then when you go into the index to find the page where you will find the phone number you are doing so at a certain speed due to the pages of the Index. Then you have to drive through the pages to get to the number. Now if your index is twice as large and the pages twice as many, then it takes longer to access the data. Now DRAM has a Strobe and the length of the strobe is how long the rows and columns can be left open before they must be refreshed. There is not enough time for the dram to be refreshed and then accessed with 4GB at the full access speed of the DRAM. The chipsets are optimized for 2GB, not 4GB and for 2 DRAM slots, not 4 DRAM slots populated. You can overclock the FSB (and hence the Memory Controller Hub = MCH) to gain some extra bandwidth and thus access the capabilities of the DRAM since the chipset is now clocked up. Usually when you clock up the FSB and concurrently the Memory Controller Hub (MCH) you need to raise the voltages of the CPU/MCH a bit as well.