Kernel Parameter "mem" - meminfo Disparity

[Matt Roth]

List members,

I have a Dell PowerEdge 6850 running Fedora Core 3 with 12 GBytes of 
RAM.  Due to limitations of a PCI card I'm installing, I wish to limit 
the system memory to just under 4 GBytes using the kernel parameter 
"mem".  When I do this, the machine boots fine and the PCI card operates 
properly, but "/proc/meminfo" and "free" report 2.6 GBytes of available 
memory.

Can anyone explain this situation or help me resolve it?  If you need 
anymore information than I have supplied, please request it.

System information:
uname -a
Linux immlx15.imm1 2.6.12-1.1376_FC3smp #1 SMP Fri Aug 26 23:51:16 EDT 
2005 x86_64 x86_64 x86_64 GNU/Linux

/proc/cmdline
ro root=LABEL=/ quiet mem=4095M

/proc/meminfo
MemTotal:      2809040 kB
MemFree:       2693600 kB
Buffers:         13308 kB
Cached:          35052 kB
SwapCached:          0 kB
Active:          42056 kB
Inactive:        29236 kB
HighTotal:           0 kB
HighFree:            0 kB
LowTotal:      2809040 kB
LowFree:       2693600 kB
SwapTotal:     2096472 kB
SwapFree:      2096472 kB
Dirty:              60 kB
Writeback:           0 kB
Mapped:          28440 kB
Slab:            19728 kB
CommitLimit:   3500992 kB
Committed_AS:    48392 kB
PageTables:       1740 kB
VmallocTotal: 34359738367 kB
VmallocUsed:    275932 kB
VmallocChunk: 34359461883 kB
HugePages_Total:     0
HugePages_Free:      0
Hugepagesize:     2048 kB            

free -k
             total       used       free     shared    buffers     cached
Mem:       2809040     115136    2693904          0      13348      35012
-/+ buffers/cache:      66776    2742264
Swap:      2096472          0    2096472       

Thank you,

Matthew Roth
InterMedia Marketing Solutions
Software Engineer and Systems Developer