OSDev.org

I traced the function 0xE801 from int 0x15, which should give the memory size by groups :
CX gives the number of Kb between 1 and 16 Mb (15 Mb is the max <=> range [1 Mb;16 Mb[)
DX gives the number of 64 Kb blocks between 16 Mb and 4 Gb ( range [16 Mb;4 Gb])

it gives these results on my test machine : CX=0x3C00 & DX=0x100 which gives a total of 32768 Ko (+1 because of the first Meg) which is the correct amount of memory.

This functions is composed of a sequence of
[pre]DB 66h

and

CS:
DB 66h
[/pre]

Can anyone explain me what are these opcodes ? and how to use them ?

I'm not quite sure what you are asking, but if it's how the BIOS function works, look at the Bochs BIOS sourcecode.

K.J.

hi,
thats is needed cause the bios is using 32bit registers/data in a 16bit code segment! (correct me if I'm wrong anyone)

Your right.

66 is the modifier for 32bit registers in a 16 bit segment and vice versa (I believe).

Would be suprised if this function works in protected mode though.