A couple of commands to answer this:
dmesg | grep memory(this will fail once the system has been up for a while and it has scrolled out of the message buffer)
sysctl -h hw.physmem hw.realmem hw.availmem(use Google if you need an explanation of what those mean)
sysctl -d which will give you a brief description of what the sysctl means.
Or just use
sysctl -dwhich will give you a brief description of what the sysctl means.
# sysctl -d hw.physmem hw.realmem hw.usermem
real memory 85899345592 (8192 MB)
avail memory 1941647360 (1851 MB)
Seems like something is very wrong!
Great in theory, not so good in practice (on 10.3 amd64):
It's normal for avail to be a bit lower than real, but that does seem extreme. I take it your physical hardware config really is 8GB? This may be a silly question, but you are running the amd64 build of the OS, and not the i386 build? (Running a 32-bit OS on 64-bit hardware is the first thing that springs to mind when I see a bit under 2GB memory available like that, but it's just a guess.)
Actually your right. I'm running an i386 version from a USB drive, but there definitely is something wrong with the memory.
Would the amd64 version even boot if there was less than 4GB?
I'll probably reboot with just one module and then test the other.
If the only reason for believing there is a problem with the RAM is the low reported avail memory, the root cause may well be solely down to running an i386 build. If you have some other reason to believe there is a problem with the memory, some details might help get better suggestions.
It would appear that I have a motherboard problem..
I took out one memory module and got the same amount of available memory as before, then I replaced that module with the other one and got the same amount. When trying either module in the other slot the system would not even boot, not even any beeps, which is strange because without any memory at all there were lots of beeps.
If you were continuing to use the i386 build of FreeBSD, it is no surprise that available memory is low.
As with most motherboards, having the first memory slot empty is an invalid hardware config. See page 2-5 onwards of ftp://ftp.supermicro.com/CDR-X10-UP_1.13_for_Intel_X10_UP_platform/MANUALS/X10SBA.pdf
Have you tried booting it with FreeBSD 10.3 amd64 yet? If not, please try that with both memory modules installed.
I was happily running an amd64 version until around 3 months ago when I found it would no long boot - there was some trap error
What kind of memory modules are used? Brand, size, speed, voltage, or what is printed on them?
Did you tried a single module in DIMM Slot 1 (right beside the CPU) while booting FreeBSD 10.3 amd64?
Was the system active cooled?