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I know that it is possible to enter in unreal mode to set the segment register ds, es to use 4GB offset. But is it possible to do that also for cs?! So should be possible to execute code also in extended mem, without the limit of the 640KB conventional memory of real mode...

this seems hard to achieve as a large (32bits) code segment also means a different decoding of opcodes (inverted db 66 and db 67)

but i never tried it, so maybe it could work anyway ...

no, since that would mean you would be in protected mode and not unreal mode.

drizzt wrote: I know that it is possible to enter in unreal mode to set the segment register ds, es to use 4GB offset. But is it possible to do that also for cs?! So should be possible to execute code also in extended mem, without the limit of the 640KB conventional memory of real mode...

All unreal mode does is fool the processor in real mode into thinking the limit of an offset isn't 0xFFFF. Nothing more. This lets you address memory at seg:off using 32-bit registers. The value of the segment register is still same as ever. And IP is still limited to 0xFFFF.

Thanx...