Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.1 6/24/83 v7 ucbopal-1.9 BSD 4.2; site ucbopal.CC.Berkeley.ARPA Path: utzoo!watmath!clyde!burl!ulysses!allegra!bellcore!decvax!ucbvax!ucbtopaz!ucbopal!edmoy 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 ucbvax!ucbopal!edmoy