Missing memory?

[Gavin Atkinson]

I have FreeBSD on an Ultra 5, and it does not seem to detect all my ram...
Am I overlooking something obvious? The machine has 64 meg of ram, but
FreeBSD only finds 39 meg (and only 33 meg is usable). Where does the
other 24 meg go? I've included the relevant parts of a dmesg, verbose
reveals nothing extra. I'm assuming the kernel etc accounts for the
difference between "real" and "avail" memory, but I cannot figure out
where the rest of my memory goes. Any suggestions?

Sun Ultra 5/10 UPA/PCI (UltraSPARC-IIi 270MHz), No Keyboard
OpenBoot 3.11, 64 MB memory installed, Serial #10249974.
Ethernet address 8:0:20:9c:66:f6, Host ID: 809c66f6.

[snip]

FreeBSD 5.0-CURRENT 4: Wed Apr 30 17:20:49 BST 2003
    root at leeloo.york.ac.uk:/usr/obj/usr/src/sys/GENERIC
Preloaded elf kernel "/boot/kernel/kernel" at 0xc048e000.
Timecounter "tick"  frequency 269833437 Hz
real memory  = 41181184 (39 MB)
avail memory = 34758656 (33 MB)
cpu0: Sun Microsystems UltraSparc-IIi Processor (269.83 MHz CPU)

Thanks,

Gavin