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From: gillies@p.cs.uiuc.edu
Newsgroups: comp.sys.ibm.pc
Subject: Re: Why is DOS limited to 640K?
Message-ID: <75800076@p.cs.uiuc.edu>
Date: 20 Oct 89 00:40:59 GMT
References: <10253@cbnews.ATT.COM>
Lines: 14
Nf-ID: #R:cbnews.ATT.COM:10253:p.cs.uiuc.edu:75800076:000:588
Nf-From: p.cs.uiuc.edu!gillies    Oct 18 20:24:00 1989


Re: Limitations of DOS and Bill Gates's mind.

Was Microsoft responsible for the PC's original BIOS?  If so, perhaps
this is why people began writing to display memory in the early days
of the PC....

An undergrad in the MIT PC/IP project was trying to implement telnet
on a PC (in 1982..).  The screen update was terribly slow, until he
looked at the BIOS and found that IBM PC's were doing 2K byte copies
to scroll the monochrome screen 1 line.

The solution was simple.  Write 5-10 lines of assembly code to use the
HARDWARE SCROLL CIRCUITRY built into the display chip on the IBM PC.