copy extended memory.

Eric W. Biederman ebiederman at
Sat Oct 26 11:02:00 CEST 2002

Adam Sulmicki <adam at> writes:

> hello,
> 	can anyone point me to an documenation on bios's
> 	interrupt 15, ah=87. It is 'copy extended memory'.
> 	I suspect the implementation I have is  wrong, and
> 	thus stops me from adding support for legacy
> 	applications under LinuxBIOS.
> 	Going over phoenix manual and Ralf Browns's
> 	interrupt list, I know that
> 	CX     = counter
> 	ES:SI  = pointer to GDT
> what is not clear to me is what does determine source and destination
> of the copy. Would it just copy between first and second segment
> (if so why it is not documented).

I have in my documentation the following addtional information.
CX is a count of works (2 byte quantities)  With the max being

And the format of the GDT is:
GDT location
source GDT entry
target GDT entry

This code works for a 286 so it has a 16MB limit.  And segments
are limted to 64K, if my memory serves me correctly.


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