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,

Hi

In article <e2e95126-f2be-42eb-9050-
>, 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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