From: shadow{at}shadowgard.com

On 5 Aug 2004 at 22:12, Norman C. Leet wrote:

> Does anyone know the history of how 7C00h came to be the
> particular address where int 19h loads the disk boot sector to 
> to memory?

I wouldn't be surprised to find that it goes bsack to the early days 
of CP/M. CP/M 1.x would run on a system with only *8k* of RAM. Later 
versions required more RAM. I note that 7C00h is 1024 bytes before 
the end of the first 32k of RAM. 

That gives you room to load two MS-DOS sectors at the "top" of RAM on 
a 32k system (which was probably the minimum that DOS required way 
back when)

--
Leonard Erickson (aka shadow)
shadow at shadowgard dot com




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