RedHat AS2.1 OS failed to see all RAM

[Victor Bao]

Background:
We have 4 HP (Comapq) Prolient DL580 servers, running ReaHat AS2.1

Two of the servers have 2 CPUs on each box, running Enterprise Kernel. The other two are single CPU, running single CPU kernel

All boxes have 5GB RAM installed.

Problem:
While server booting up, full size of RAM (5120MB) are recognized by the POST test.

After booting up, free command has below output:
on dual-CPU servers--
total used free shared buffers cached
Mem: 4889996 579688 4310308 476 219644 204296
-/+ buffers/cache: 155748 4734248
Swap: 2096440 0 2096440
on single-CPU servers--
total used free shared buffers cached
Mem: 3859512 2800244 1059268 516 235852 2373944
-/+ buffers/cache: 190448 3669064
Swap: 2096440 0 2096440

I understand the Enterprise kernel can support 16GB RAM without any customization,and the basic kernel can support up to 4GB RAM.

So we are just wondering --
why we can not see exactly 5120MB RAM on Enterprise kernel ? (4889996KB=4775MB)

why we can not see exactly 4096MB RAM on basic ? (3859512KB=3769MB)

Since hardware selftest indicated 5120MB, we think the above problem should go to OS side rather than hardware side.

Please advice.

Thanks

Victor Bao

[Jon_87]

The UP kernel is probably built for 4giga, SuSE for example shipps 4giga UP and 64giga SMP. ON the UP server you can either build this into the kernel or try the SMP kernel and send a boot parm = nosmp