Intel GMCH 82815

[ali hagigat]

I am working with Pentium III, Intel GMCH, 82815 and Intel ICH2, 82801.

I managed to initialize DRAM controller to recognize the first 640 K
of the memory correctly in the real mode.

When i switch to the protected mode, CPU writes to the first 64K only.
Every other read/write from the higher addresses leads to CPU restart.

Can anybody say what is going on?