Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.2 9/18/84; site uw-beaver Path: utzoo!watmath!clyde!burl!ulysses!mhuxr!ihnp4!houxm!vax135!cornell!uw-beaver!info-mac From: info-mac@uw-beaver Newsgroups: fa.info-mac Subject: high byte of address question Message-ID: <456@uw-beaver> Date: Fri, 18-Jan-85 04:46:04 EST Article-I.D.: uw-beave.456 Posted: Fri Jan 18 04:46:04 1985 Date-Received: Sat, 19-Jan-85 01:03:01 EST Sender: daemon@uw-beaver Organization: U of Washington Computer Science Lines: 17 From: edmoy%ucbopal.CC@UCB-VAX 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