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IBM PC XT/AT and memory holes

I tried to find a copy of the original specifications document for the
IBM PC XT/AT, but I wasn't able to. I wanted to know what was the
memory map of the original IBM PC XT.

I remember reading that the regions from 0xA000:0 till 0xFFFF:7FFF
were reserved for something other than memory mapped IO.

Did the concept of memory mapped IO exist in the PC XT at all?

Thanks,
0
Vimal
8/26/2008 7:32:02 PM
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Hi

In article <e2e95126-f2be-42eb-9050-
71b8e40e278c@v26g2000prm.googlegroups.com>, j.vimal@gmail.com says...
> I tried to find a copy of the original specifications document for the
> IBM PC XT/AT, but I wasn't able to. I wanted to know what was the
> memory map of the original IBM PC XT.
> 
> I remember reading that the regions from 0xA000:0 till 0xFFFF:7FFF
> were reserved for something other than memory mapped IO.
> 
> Did the concept of memory mapped IO exist in the PC XT at all?
> 
> Thanks,
> 
you might want to ask the question in comp.sys.ibm.pc.classic

the memory hole you're referring too did exist , from memory, it was 
between 640k(base memory) -- (upper memory) 1024k, this address was 
reserved for other I/os such as mono graphic cards, bios, hd bios 
(rll,mfm)and others.....

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0
Cheers
8/28/2008 10:15:03 AM
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