[comp.os.msdos.programmer] Int 15h function 88

kushmer@bnlux1.bnl.gov (christopher kushmerick) (04/11/91)

My AT has 2.5 mbytes of extended memory starting just above the one
megabyte position, and 0.5 megabytes at $A00000. The letter is for
a frame grabber.

When I do int 15 function 88 (count extended memory), only the 2.5 mbytes
seems to get counted.

Does this mean absoultly that I will not be able to use int 15 function 87 to
read and write that other 0.5 Mb at $A00000?


-Chris

-- 
Chris Kushmerick                                 kciremhsuK sirhC
kushmer@bnlux1.bnl.gov    <===Try this one first
kushmerick@pofvax.sunysb.edu 

rcollins@altos86.Altos.COM (Robert Collins) (04/12/91)

In article <1991Apr10.215111.12959@bnlux1.bnl.gov> kushmer@bnlux1.bnl.gov (christopher kushmerick) writes:
>
>My AT has 2.5 mbytes of extended memory starting just above the one
>megabyte position, and 0.5 megabytes at $A00000. The letter is for
>a frame grabber.
>
>When I do int 15 function 88 (count extended memory), only the 2.5 mbytes
>seems to get counted.
>
>Does this mean absoultly that I will not be able to use int 15 function 87 to
>read and write that other 0.5 Mb at $A00000?
>

INT 15, FN 88 doesn't really count extended memory.  It simply looks in
CMOS to see the amount of available extended memory.  This is really
brain-dead, but you wouldn't want INT15 to actually resize memory each
time, and possible crash some data in the process.  So it simply looks
in CMOS and returns the available extended memory in KB.

You may still use FN87 to access your memory @ A00000 because FN87 
requires you to provide a descriptor table with the addresses of memory
you require to access.


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