Can anyone explain this?

[Azuse05]

I've got 4x1GB sticks of ocz 800mhz ddr2 (4-4-4-15). One set is 3 years old, the second - just - 1 year old, because I got it new from an rma this time last year.

Now over the past month I've had the occasional failed post and the odd corrupt download but the memory always passed memtest. Last week it stopped posting. After some tinkering it seemed the bios had set the ram at 1.8v after me removing it so I put it back to the rated 2.1v and things went well.

Machines stopped posting after a couple days but I'd switched motherboards over the weekend, and after ruling out my own mistakes I nailed it down to one of the stick from the second set. If it was in either motherboard, no post. Just lights, fan and noise but nothing more.

Now, the thing is if it's in the machine then sometimes it posts, sometimes I press the power it switches on, then immediately off then back on and boots. If I leave it in and the pc off overnight then it will fail post in the morning (sometimes) or if I pull all the ram out, leave it off for 2 min then put the offending stick in alone, no post.

I want to ram it again, but seeing as it passes memtest - when it boots - can I? Better, why does this stick behave like this?

 

[firewallblocked]

I did have some 2nd hand GeIL memory and that would always boot and run but cause random crashes, sometimes after an hour or so, passed memtest ok but in the end I stopped using once it was obvious it was causing the instability.

How long did you try memtest for? I run it for a few hours sometimes when I'm uncertain if it faulty memory. I believe the latest versions of memtest don't just keep testing until you stop it like the old versions.

Have you checked you psu to be certain it's 100% ok. When you test each stick at a time do you always use the same slot each time and have you tried your pc running for a few days with what appears to be the 3 good sticks. Just to see if it's stable.