Resolved Odd memory problem (partial intermittant disappearance)

I have an i7 960 with 6GB of memory.

Or at least, sometimes it has 6GB of memory.

Lately it's started booting, sometimes with 6GB and sometimes with 4GB. As memory has to be used in sets of 3 with this m/b (and it shouldn't work with only 2 modules) I find this particularly puzzling.

The OS is W7 64bit Pro. The memory figure is coming from Task manager and Control Panel | System.

 

Sorry, I should have mentioned that it's been running quite happily for 6 months so I doubt it's incompatible - not impossible but not likely, particularly as I actually bought the PC ready made (A first in nearly 30 years) from a reputable supplier.

It's not overclocked.

Incorrectly seated would have been my first thought but, as I said, you have to add memory three banks at a time with this m/b and processor so I can't make out how the system could possibly work if that (or, indeed, the other two possibilities you mention) were the case.

Since the system should not work at all with only 2 banks of memory installed/working I assumed it might be a W7 peculiarity which was why I initially posted this in the W7 forum.

 

That is not true. It will work fine with just 1 or 2 modules. BUT, in order to take advantage of triple (or dual) channel memory architectures, you must have a complete complement of modules, and they must be installed in the proper slots.

 

Yes. I realised after Arie ignored that statement twice that it needed further checking and discovered what I'd been told by the company that built the machine was wrong.

It was that misconception that caused me to believe it might be some (very) odd W7 configuration problem, simply because in cases where memory must be installed in multiples the system fails to function at all if not correctly populated. Otherwise the very first thing I would have done was re-seat the memory, a course of action which appears to have cured the problem (as it so often does ).