Memory over 1 gigabyte not seen by Knoppix, BIOS sees it

I'm working with a hard drive installation of Knoppix that boots into twm for a specific project. The hard drive installation and remastering is all going well, BUT the problem is this:

The BIOS reports 2048 MB of RAM which consists of 4 512MB memory modules. However when Knoppix boots up, it only reports a total of 904,948K of memory, far from the 2 Gigabytes worth installed. When only 2 of the 4 512MB chips are installed (any combination of the 4 modules), Knoppix remains the same with approx 1 Gig reported (top) while the BIOS reports it correctly as 1024MB.

My question is, has anyone installed over 1 Gig of memory successfully under Knoppix and is there anything that may LIMIT total memory to 1 Gigabyte?

Thanks

Yes, I recompiled the kernel with the flags

CONFIG_HIGHMEM4G=y
CONFIG_HIGHMEM=y

in order to get the last few mb of my 1Gb. Otherwise you only get what you saw.