How much ram will Windows Memory Diagnostic test?

[nine9s]

Does Windows Memory Diagnostic test 8GB (2X4GB) memory? It does not show how much ram you have while running and I cannot find any officials sources confirming. I found some Ask.com article stating that a con of it is that it only tests 4GB but no Microsoft source listed or anything.

Anyone know any official confirming of any memory size limits for it?

 

[nine9s]

I found some websites stating that the ISO Windows Memory Diagnostic is 32-bit and warns it cannot test all memory when it runs if you have over 4GB. While the one built into a X64 Windows 7 is 54-bit and does not show such warning - when I ran it, I saw no such warning.

Anyone know if the built-in one handles over 4GB?

 

[ZeroRift]

When I first built my rig I used that tool (among others) to test 4GB of memory. It took about the same time to run through as the aggressive settings of memtest86, as I recall.

Later, I upgraded to 16GB and it took WAY longer to test than when I had 4GBs (difference of ~2hrs to having to run it overnight). I also broke the test up into 4GB chunks (1 DIMM at a time) and each took about a quarter of the time of the whole 16GB set.

Sure looks like it does if you have a 64bit OS.