Strange Memory Errors

[marktwayne]

I bought a Dell Optiplex 755 second hand in 2014. I upgraded two 1 GB ram modules with 4 Dolgix 2 GB DDR2 800 MHz modules for a total of 8 GB. I also upgrade the processor to Core2 Quad. It ran the system for two years fine until I started getting BSOD's with errors suggesting RAM problems.

Why I don't think anything is wrong with the RAM memory -
The Optiplex 755 BIOS has a built in memory scan. I only get memory errors when I have more 2 or more sticks installed. I've run each individual stick for hours without ever finding an error. I've even tried the two Samsung 1GB DDR2 667 MHz memory modules originally shipped with the computer. That pair tests with errors, but alone each stick tests fine.

Why I don't think it is the processor -
I have several LGA 775 processors compatible with the computer. I get the same memory errors whether I have the Core2 Duo E6550 or Core2 Quad Q8400S installed. I have monitored the processor temperature, and I haven't seen it warmer than 69 degrees Celsius.

Why I don't think it is the motherboard -
I was able to find an identical motherboard on eBay sold as new in a sealed bag, so I replaced the motherboard with this new one and get the same memory errors. Two motherboards are unlikely to have the same problem. In both motherboards, the RAM tests fine as long as it is a single piece. The BIOS is A22, the latest version.

What else is eliminated?
RAM tests are at BIOS level. I've run the tests with the hard drive removed, with failing results if more than one piece of memory is in. Hard drive and OS is eliminated as a factor.

What is left?
Power supply could be a factor after I've eliminated just about everything else. Is it possible that the power supply might be responsible for this? Unfortunately the power supply is proprietary and I don't have a duplicate.

I'm currently running the computer on a single 2 GB stick. It has been running stable like that for a week, but I'd like to get back to running on 8 GB. Am I missing anything?

 

[geofelt]

memtest86+ is the gold standard for testing ram.
You should be able to complete a full pass with NO errors.

Ram is sold in kits for a reason.
A motherboard must manage all the ram using the same specs of voltage, cas and speed.
Ram from the same vendor and part number can be made up of differing manufacturing components over time.
Some motherboards can be very sensitive to this.
This is more difficult when 4 sticks are involved.
That is why ram vendors will NOT support ram that is not bought in one kit.

Also, the construction of a stick itself may make it incompatible with some motherboards.

My suggestion is to go to a ram vendor web site and access their ram configurator.
Enter your motherboard and you will get a list of compatible kits.
Buy a 2 stick kit which will cost less and perform the same as a 4 stick kit.

Most ram will have a lifetime warranty.
You could try the rma procedure for each kit that does not test properly.
You can try to rma

 

[marktwayne]

Thanks for responding.

My original post made it clear that I bought a kit with four sticks of ram two years ago and I had no errors until just recently. This rules out the differing component theory, and possibility of incompatibility.

"Buy a 2 stick kit which will cost less and perform the same as a 4 stick kit."

Purchasing 8 GB in 4GB-per-module memory kits is very expensive. A 2x4GB memory kit (compatible with my motherboard) costs about $100. A 4x2GB kit costs about $30.

My memory has a one-year warranty. I purchased it about two years ago.

I've already ordered and replaced the power supply and memory for $45. My system is running fine now.