Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!sun-barr!lll-winken!uunet!mcsun!ukc!mucs!logitek!alanh
From: alanh@logitek.co.uk (Alan Hourihane)
Newsgroups: comp.sys.atari.st
Subject: AT Speed & Protected Mode
Keywords: AT Speed
Message-ID: <alanh.665151775@krypton>
Date: 29 Jan 91 12:22:55 GMT
Distribution: comp
Organization: Logitek Plc.
Lines: 30

Remember AT Speed & Protected Mode.

	Well, it looks as though I have found the problem.

	In the AT Speed manuals, it says it supports BIOS functions 87HEX and
88HEX via the INT15 call, These calls relate to shifting blocks of memory
especially into extended (i.e. above 1 Meg). To switch the processor into
protected mode the function call 89HEX is made via INT15 again. This in turn
crashes AT Speed.

	With 87HEX and 88HEX it does not switch the 286 into protected mode,
but passes some code onto the 68000 to shift the block of memory, rather
than get the 286 to do it.

	This is also why windows 3 works because it only uses calls 87 and 88.

	So, any program out there which works under DOS and switches the
processor into protected mode via function call 89HEX will crash, subsequently
OS/2 and XENIX will not function either.

	Therefore the features of AT Speed over PC Speed, that I can only see
is the Speed increase from 4.4 to 6.7(Norton Factor).

	CAN ANYBODY FIX THIS ??????????


	Thanks.  

	e-mail:alanh@logitek.co.uk