4GB on 32-bit Debian?

sycamorex · 07-03-2007, 05:34 AM

Hi all,

I've got Debian Etch (32 bit). I have recently upgraded my RAM to 4GB.
However, it only recognises 3.2 GB. In BIOS it recognises full
4gig and states that they are 'fully usable' so everything seems
ok there.

I've read somewhere that it's a problem of a 32-bit version of a kernel
on Debian, and that 64-bit version would solve the problem. Is it true?

thanks

Telemachos · 07-03-2007, 06:05 AM

Do you have the large memory (bigmem) kernel installed? I think that for that much ram, you would need it. Do a 'uname -r' to find out your current kernel, and then try "aptitude search linux-image" to see if you can find the appropriate bigmem version.

Dutch Master · 07-03-2007, 06:24 AM

Keep in mind that the kernel sees 1 kb as 1024 byte, whereas any vendor sees 1 kb as 1000 byte. That means that 1 GB is actually 1,073,741,824 bytes and not 1,000,000,000 bytes. Do the rest of the math yourself

sycamorex · 07-03-2007, 07:20 AM

Quote:

Do you have the large memory (bigmem) kernel installed?

Thanks for the replies, Yes, I've definitely got the Big mem option enabled in the kernel. I checked the config file. Anyway If it wasn't, it would only recognise up to 1GB. Btw, it's 2.6.18.4-686 kernel

As to the maths issue, I'm not a mathematician, but that would suggest that I should have around 3.8Gb recognised by the kernel, not 3.2 (btw, my graphics has separate memory, so it doesn't use the main ram)

thanks

lycan · 07-03-2007, 09:56 AM

Quote:

Originally Posted by sycamorex

Hi all,

I've got Debian Etch (32 bit). I have recently upgraded my RAM to 4GB.
However, it only recognises 3.2 GB. In BIOS it recognises full
4gig and states that they are 'fully usable' so everything seems
ok there.

I've read somewhere that it's a problem of a 32-bit version of a kernel
on Debian, and that 64-bit version would solve the problem. Is it true?

thanks

You guessed right. You cannot use 4GB RAM on a 32 bit system. The system always recognizes around 3-3.2 GB, not 4GB. Its a restriction of 32 bit OS regardless of windows and *nix systems. You have only two options.

1. Install a 64bit version of debian.

2. Recompile the 32 bit kernel with extended memory support or whatever it called( I can't remember the phrase exactly ).

sycamorex · 07-03-2007, 10:44 AM

Thank lycan,

I'll try to recompile the kernel. does anyone know the exact name of the parameter in the kernel?

regards

HappyTux · 07-03-2007, 11:52 AM

Quote:

Originally Posted by sycamorex

Thank lycan,

I'll try to recompile the kernel. does anyone know the exact name of the parameter in the kernel?

regards

Recompiling will make no difference it is a hard limit of 32bit and the way the memory is mapped using the options in your BIOS, PAE and the space reserved for your PCI devices/video card. In other words you getting all you can right now unless you use a 64bit install addressing the memory with 64bit mode enabled in your BIOS then you will see it all.