Gentoo don't detect full ram memory
 

Hi;
I can't make Gentoo recognize my 2 rams of 512MB, It's seems to recognize just 891900 KB:
I tried to recompile the kernel with 4gb ram support but I couldn't find the "High memory support" in "Processor type and features", I think because I have a amd64 OS.

Kernel version: linux-2.6.30-gentoo-r3
RAM: hynix 512MB HYMP564U64CP8-Y5 (Specification are here in PDF)


Thanks in advance

Are you using a video card which uses your system RAM? Laptops or motherboards with onboard gpu's take up a portion of your system RAM to use as Video RAM (VRAM)

But windows vista detect 1GB!

That's a good guess. But it is easy to determine whether this is a Linux problem, so no need to guess.

Try
If it is soon enough since the last reboot that the message buffer hasn't wrapped you should find near the top something looking similar to:

That last number (where my system has bfe8ac00) or maybe a subsequent line saying "usable" if your memory map is strange, tells the limit of the memory that the BIOS makes available to Linux.

If the difference is video ram or some BIOS or motherboard issue that value will be too low.

If the problem is a build time option in your Linux kernel, that number should be correct.

Since there are a number of details that might be confusing, I suggest you post that memory map from your dmesg so I or someone else can tell you what it means.

Meanwhile, someone who knows Gentoo kernel details probably can tell from just what you posted already whether this is the result of a kernel build time choice and if so where to get or how to build a kernel without that restriction. But I don't know Gentoo and I need to see the memory map to know whether the problem arises before Linux loads or inside Linux.

Do you really? If you have an amd64 OS then the problem is not a kernel build time issue, and it is almost impossible for it to be any Linux issue (so the memory map will show us it is a video ram or BIOS or motherboard issue).

But try
to see if you really have an AMD64 OS. I'm pretty sure the output will include "x86_64" (probably 3 times) if it is an AMD64 OS and it certainly won't include "x86_64" if it is not an AMD64 OS.

Vista lies about how much ram it detected, so that really doesn't tell us much.

This is it:
And I found this too (I don't know if it will help):

I actually did somethings more complicated than that so I think I'm pretty sure about my architecture...

Thanks

So the BIOS makes only 893.185 MB of ram available to Linux.

The big reserved chunk at 37000000 is probably video memory and probably the reason for almost all the difference between the 1024MB you should have and the 893MB you do have.

That just takes a tiny bit away from the 893.185MB, not enough to worry about at all.

Not showing the uname output may still leave people not believing you know your architecture. But it doesn't matter. We see from the dmesg output that the memory is lost before Linux even starts, so nothing about your kernel or architecture is relevant.

tkbonito's theory is looking pretty solid at this point.

So that's it...

Thanks for helping anyway ;o)

I recommend install lshw and post the results. This will show in depth what your computer actually contains.

A 893 MB of RAM does relate to some kind of video memory being used. Though 128 MB of memory that can not be used could be a stupid memory hole feature that has been enabled.

Gentoo's kernel patches are not any different than the vanilla kernel. I have not experience any memory problems when using gentoo-sources as the kernel. If the vanilla kernel has a memory problem, so will every patch will have the problem.

Sorry for being so late...

well this is the results of lshw :
Thanks