Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!rice!uupsi!grebyn!ckp From: ckp@grebyn.com (Checkpoint Technologies) Newsgroups: comp.sys.amiga Subject: Re: SVR4 vs OSF/1 (Was Re: A3000UX competition) Message-ID: <23913@grebyn.com> Date: 10 Dec 90 17:20:42 GMT References: <2346@lpami.wimsey.bc.ca> <1990Dec7.201504.11469@Neon.Stanford.EDU> <599@amix.commodore.com> Reply-To: ckp@grebyn.UUCP (Checkpoint Technologies) Organization: Grebyn Timesharing, Vienna, VA, USA Lines: 23 In article <599@amix.commodore.com> ford@amix.commodore.com (Mike "Ford" Ditto) writes: >In article mwm@fenris.relay.pa.dec.com (Mike (My Watch Has Windows) Meyer) writes: >>of AmigaDOS: [ ... ] user-mode mountable (and dismountable) >>device drivers; > >I'll have to disagree there. AmigaDOS does NOT have user-mode device >drivers. AmigaDOS does not have user-mode anything. In AmigaDOS, >every byte of code that ever runs runs in the equivalent of kernel >mode, with access to every bit of physical memory and every hardware >register. [ rest deleted ] Others will disagree with you. IO is done by Exec "tasks" (or ADOS "processes"), which run with the PSW set to "user mode", not "supervisor mode". However, I have to essentially agree. IO space is addressable while in "user mode", and the only other thing the supervisor mode can do, disable interrupts, can be done easily in user mode by poking the Paula INTENA register (indeed, this is the system-defined way to control interrupt delivery). -- First comes the logo: C H E C K P O I N T T E C H N O L O G I E S / / \\ / / Then, the disclaimer: All expressed opinions are, indeed, opinions. \ / o Now for the witty part: I'm pink, therefore, I'm spam! \/