[Japo]

You may well be right, although unfortunately Dell doesn't provide proper documentation at this level. I think it's a (possibly customized) Intel motherboard, but I'm not sure which one. According to Memtest86+ and HWiNFO it may be "x48", which apparently has 8 GB max. At Intel.com it wasn't recognized as Intel.

But at any rate it does seem to accept 4 GB sticks. With 8 GB I think I've worked long enough to be sure that there are no problems. Nevertheless this might explain my issues while using 10 GB (2x4+2x1), as well as the diminished tallies (11.9 GB instead of 12 and 14.7 instead of 16). I'll be on the alert in case any problem comes back with 12 GB, then I'll know what to expect.

Thanks.