Ubuntu :: 10.10 64-bit Shows 3.7GB Out Of 4GB RAM On Laptop With Dedicated Graphics?

I'm accustomed to Ubuntu showing 3.9GB out of 4GB on my desktop. That's completely ordinary and expected: The kernel uses a dozen megs or so, which are not accounted for in the reported memory totals. After truncating, that brings us to 3.9GB.

I was expecting to see the same thing on my Elitebook 8740w, but System Monitor is reporting only 3.7GB instead, using the same version of Ubuntu. free -m shows:

total used free shared buffers cached
Mem: 3819 935 2883 0 80 287
-/+ buffers/cache: 567 3252
Swap: 4095 0 4095

That is to say, the total of 3819MB is not missing a mere dozen or so MB but a full 267MB from 4096MB! That's WAY too much to be accounted for by the kernel, so something else is going on!

Please note the following:BIOS shows the full 4GB, and so does lshw.

uname -a = Linux COMPNAME 2.6.35-22-generic #35-Ubuntu SMP Sat Oct 16 20:45:36 UTC 2010 x86_64 GNU/Linux
lspci | grep VGA = 01:00.0 VGA compatible controller: ATI Technologies Inc Broadway XT [Mobility Radeon HD 5800 Series]

That is to say, I really do have 4GB RAM, my mobo and BIOS recognize it, I really am running a 64-bit OS, and I really shouldn't have any kind of onboard graphics.

The devil lies in the details though: I SHOULDN'T have any kind of onboard graphics...but the best explanation I can come up with is that 256MB or so are being set aside for that purpose anyway. This is a mobile workstation with dedicated Firepro graphics (based on the Mobility Radeon HD 5800), and it's well beyond the range of laptops that include switchable graphics. However, it has an i5 processor, so I think it's conceivable that the laptop is being tricked into allocating RAM for integrated graphics. This is especially likely considering I get the same i915 error as the threadstarter here, and I have very similar command line output.

Presumed Problem: Long story short, I think Ubuntu is seeing the i5 processor and setting aside 256MB or so for the integrated graphics which it THINKS I have, which are actually totally unavailable to use on this particular laptop. If this is the case, does anyone know how to make it stop doing this, so I can make that memory accessible to the rest of the system?

Update: Interestingly, even Memtest is showing only 3952MB. This may or may not account for the full missing amount, but it obviously counts for a lot. I'm used to Memtest showing I think 4095MB on my desktop, meaning Memtest itself presumably only takes ~1MB. Actually, even on the laptop Memtest says only 1024KB are reserved, so 143MB are totally unaccounted for.