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[Japo]

So I wanted to expand my RAM. My computer has four slots and I was running with 2x4GB, and before that with 4x1GB which was the OEM's configuration. I had tried mixing 2x4GB+2x1GB but it caused freezes (incompatible RAM timings maybe?). I bought another pair of 4GB sticks, as identical to the two I had as absolutely possible without being made the same day, and from the same manufacturer.

When it's time for Windows to start, the computer just freezes. I have Vista x64 Home Premium, whose top is 16 GB precisely. And besides from what I've read if you surpass these limits Windows works just the same, but with capped RAM.

It doesn't seem to be due to my Windows installation, as the same happens with the bootable installation DVD.

With 12 GB for example Windows works OK, although Windows reports 11.9 GB (12,221 MB), but this may be unrelated. It doesn't seem to be caused by a defective stick or slot. I have swapped the sticks in place and actually it works the same if I fill DIMM slots 1-3 or 1-2 and 4. It always worked fine with the OEM configuration, which was 1 GB sticks filling all four slots.

I have run both the OEM-provided memory diagnostics and MemTest86+ with negative results. MemTest86+ for one reports 4x4096MB correctly.

The BIOS reports 16 GB in dual channel. With three sticks, which is the most I can run Windows on, it reports 12 GB in "flex mode", so everything looks fine. Although then on the detailed list the BIOS also reports any 4 GB stick as 512 MB, but that may be unrelated too. I have the latests BIOS update (from Dell, from 2009). At any rate the problem appears when Windows is supposed to enter the stage.

I have tried booting an Ubuntu CD, and it runs OK, but this time reporting 14.7 GiB...