64-bit 13.10 shows 1GB less RAM than 64-bit 13.04 did

Solution 1:

You're measuring apples and oranges.

Your kernel still sees 4 gigs of RAM. free only returns map-able RAM. You have 1 Gig of RAM that can not be accessed. This can happen because of several things, but I would guess that the update updated video drivers and that your card is "using" part of that RAM.

You may want to check that your RAM is not "marked bad" with something like BadRam.

Finally you may want to look (though I don't think this is it) to make sure the kernel isn't mapping RAM in an odd way.

cat /var/log/dmesg | grep -a 40 "BIOS-provided physical RAM map:"

should get you started down this path. Though you may try just loading the older kernel if you did an update and see.

Basically you need to figure out where the missing memory is. It's there, your system sees it, it's just mapped to something different then your used to.