Detected 3960mb of memory instead of 4096mb

[Xwang]

Hi,
I've a new laptop with 4gb of ram. I've installed kubuntu 8.10 amd 64 and both the live cd and the installed system recognize the total amount of memory ad 3960mb instead of 4096 (the bios recognizes all the installed memory). Is there a reason for such behaviour? Otherwise should I configure something to have all the memory recognized by the system?
Thank you,
Xwang

[sithlord48]

Re: Detected 3960mb of memory instead of 4096mb

my system w/ 4gb also shows 3960MB of RAM. i know that i lose 64 MB of ram due to a kernel message i get on boot. (no gfx apature setting in bios). that should give me 4032mb of ram . now where the other 72MB of ram goes i haven't a clue.(it could be reserved by the system)

[flarson]

Re: Detected 3960mb of memory instead of 4096mb

My system with 2GB reports 1986M. This is a standard behavior although I can't remember why at the moment. The kernel is taking some for itself and not reporting it.

[dibl]

Re: Detected 3960mb of memory instead of 4096mb

I have 4G of RAM installed. Kinfocenter reports "Total physical memory 4,087,554,048 bytes = 3.81G".

I think if you start with 1G = 1024M, and divide backwards (1M = 1024K, etc.), it works out.

[flarson]

Re: Detected 3960mb of memory instead of 4096mb

I won't claim to entirely understand this, but I think this is an artifact of memory mapping using mmap for faster access to larger memory, or, in the case of 32 bit, access to larger memory.
http://www.opengroup.org/onlinepubs/...ions/mmap.html

[jglen490]

Re: Detected 3960mb of memory instead of 4096mb

Hi,
I've a new laptop with 4gb of ram. I've installed kubuntu 8.10 amd 64 and both the live cd and the installed system recognize the total amount of memory ad 3960mb instead of 4096 (the bios recognizes all the installed memory). Is there a reason for such behaviour? Otherwise should I configure something to have all the memory recognized by the system?
Thank you,
Xwang

Open up a terminal and enter:

free

What does it come back with?

[Xwang]

Re: Detected 3960mb of memory instead of 4096mb

free
total used free shared buffers cached
Mem: 4055128 1038796 3016332 0 25576 458596
-/+ buffers/cache: 554624 3500504
Swap: 6000236 0 6000236

I've discovered in the logs of the kernel that it recognizes alla the memory but reserves part of it so the total which happears in free is 4096mb - reserved memory.
Now it's all clear!
Xwang

[Fintan]

Re: Detected 3960mb of memory instead of 4096mb

Hmm...
On my toshiba M800 test (before I buy) and JJ 64bit.
free shows:

total used free shared buffers cached
Mem: 3760 566 3194 0 18 233
-/+ buffers/cache: 314 3446
Swap: 2439 0 2439

The Bios says: 4096