Thanks for the response. Interestingly, i could not find any BIOS
options pertaining to memory.
I found the following.
# cat /proc/mtrr
reg00: base=0xfeda0000 (4077MB), size= 128KB: write-back, count=1
reg01: base=0xfff00000 (4095MB), size= 1MB: write-protect, count=1
reg02: base=0x00000000 ( 0MB), size=2048MB: write-back, count=1
reg03: base=0x80000000 (2048MB), size=1024MB: write-back, count=1
reg04: base=0xc0000000 (3072MB), size= 256MB: write-back, count=1
Could be incompatible memory modules or something?
Thanks
Srikanth
Wolfgang S. Rupprecht wrote:
> Srikanth Konjarla <srikanth.konjarla@xxxxxxxxx> writes:
>> I am running F7 in 64-bit mode on a laptop. I have upgraded the memory
>> from 3G to 4G (Bios confirms it) but kernel sees only 3.2G (i have
>> passed mem=4096M kernel parameter). Wondering if i am missing anything
>> here.
>
> What you are missing is the really nasty design of IBM-PC legacy
> memory allocations. ;-)
>
> Play around in your BIOS and see if you can map the excess memory
> above 4GB. Often the labels for the settings will have the term
> "MTRR" in the name. When you get it right "cat /proc/mtrr" should
> show the extra 750MBytes mapped above 4 Gigs. The setting names might
> not make much sense (at least they don't on my Tyan). You might need
> to just try them all and see what effect they have on the linux mttr
> settings. Here is what it looks like on my board when I have it set
> to see all 4 GBytes:
>
> $ cat /proc/mtrr
> reg00: base=0x00000000 ( 0MB), size=2048MB: write-back, count=1
> reg01: base=0x80000000 (2048MB), size=1024MB: write-back, count=1
> reg02: base=0xc0000000 (3072MB), size= 256MB: write-back, count=1
> reg03: base=0xcff00000 (3327MB), size= 1MB: uncachable, count=1
> reg04: base=0x100000000 (4096MB), size= 512MB: write-back, count=1
> reg05: base=0x120000000 (4608MB), size= 256MB: write-back, count=1
> reg06: base=0xd8000000 (3456MB), size= 128MB: write-combining, count=2
>
> Notice the first 3 entries are 3.25 GBytes (reg00, reg01 and reg02).
> The last 0.75GBytes are mapped above 4GByte (reg04 and reg05).
>
> -wolfgang
