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From: edmoy@ucbopal.CC.Berkeley.ARPA
Newsgroups: net.micro.mac
Subject: high byte of address question
Message-ID: <224@ucbopal.CC.Berkeley.ARPA>
Date: Tue, 15-Jan-85 22:16:00 EST
Article-I.D.: ucbopal.224
Posted: Tue Jan 15 22:16:00 1985
Date-Received: Fri, 18-Jan-85 01:45:24 EST
Organization: Univ. of Calif., Berkeley CA USA
Lines: 15

I've been playing around with sumacc C programming and had to do a little
programming in assembly language to handle some special cases.  I've
noticed that the high byte of an address (the 68000 only uses the bottom
24 bits) is used alot in the Mac for special purposes.  However, even when
I do a Load Effective Address (lea) command, the high byte is sometimes
non-zero and I have to clear it out.  Does anyone know if the hardware in
the Mac uses that high byte for something?

Edward Moy
Computing Services
University of California
Berkeley, CA  94720

edmoy@ucbopal
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