Installed 4gb DDR2 (dual channel) and find that Linux only finds about 3.3 gb. Reading around, this happens with 32 bit Windows products.

I am running a PcChips P17G/1333 board, with a Intel E2180. The memory is in 2x2gb DDR2 cards.

I'm open for suggestions.

Oh, although I consider BIOS merely a proposition, the BIOS reports similar available memory.

Has anyone been here?

You need to run a PAE enabled kernel to see anything above around 3.3GB

You may actually need to do more. I used to have an ASUS mobo that would not show more than a fraction of my RAM regardless of the type of kernel. The thing was that this type of board needs to have memory mapping enabled in BIOS to show all available RAM. But if you run a 32 kernel, you will still need to recompile it for PAE, whether your board requires memory mapping or not.

Here's a description of the issue:

http://www.linux.com/feature/119287

Using a 32-bit processor or running a 32-bit OS with a 64-bit processor on a setup with 4 GB of RAM will provide only around 3.2 or 3.3 GB of RAM for the user. The rest is used for addressing all the memory that will be used for the user. The reason for this is the stupid PAE feature that (spoiled) developers have placed. PAE just creates a mess of things for 32-bit computing with a setup of 4 GB of RAM. All 32-bit processors since 80386 can handle 4 GB with out PAE.

In order to use all 4 GB of RAM, you have to re-compile the kernel using -m64 or set an option in the kernel. A pre-compiled kernel can also be used that was compiled for 64-bit processors.

Intel Core 2 Duo processors does not work as efficiently when running 64-bit programs compared to 32-bit. In simpler terms you loose performance when running 64-bit programs on systems with Core 2 Duo processors.

Guys

If the bios is only reporting 3.3gb then this is a hardware issue and not a software issue. I suspect he has a motherboard with the Intel chipset (not cpu) that only used a 32bit memory controllers. There were a lot of 64bit cpu capable motherboards that were sold with these chipsets. If he has one of these motherboards he is just SOL. The other possibility I see is that he may have a bad stick of memory. Running memtest86 for a couple of hours should sort that out.

Memory mapping?

IF he has one of the Intel chipset boards it is the controller that is the issue(32bit). So there is no way to duck the issue. The motherboards with the memory mapping option in the Bios are a different chipset.

Ah, OK, it is just that I seem to remember (vaguely, I may be wrong) that an ASUS mobo I had would show only 3.2 without memory mapping enabled.

Yep, and that may very well be in the op's case. But if he has one of the motherboards with the chipset I mentioned he will not have that option in his bios.

lazlow, you did not mention any Intel chipset models. It is not a 32-bit memory limitation. It is how Intel design their memory controller for certain 945 models. An GZ, GC, an PL has the limitation. It is not a 32-bit issue, it is a 31-bit issue.

Yep, I could not remember the exact chipsets off the top of my head (old age) and I was to lazy to look them up. But a quick google on "intel chipset 3gb limit" reveals a lot of relevant material.

There is some convergence on the issue. The P17G/1333 motherboard uses the Intel 945 chipset. While most vendors advertise it to support 4gb, it turns out that the manufacturer specs it for 2gb.

So it's a hardware limitation. It does work with 3.3gb, and after paying less than $30 for 4gb, I'm not going to loose sleep over it.

I think it's safe to say it is a motherboard issue, and my recommendation to everyone is to read the manufacturer's manual before you buy. Even then, there can be mistakes.