Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!uunet!crdgw1!barnett From: barnett@grymoire.crd.ge.com (Bruce Barnett) Newsgroups: comp.sys.mac.system Subject: Re: Protected-mode snake oil Message-ID: Date: 17 Aug 90 16:57:55 GMT References: <1210.26c694ed@waikato.ac.nz> <8099@jarthur.Claremont.EDU> <1990Aug14.010751.20050@NCoast.ORG> <1252.26cbdffa@waikato.ac.nz> Sender: news@crdgw1.crd.ge.com Reply-To: barnett@crdgw1.ge.com Followup-To: comp.sys.mac.system Organization: GE Corp. R & D, Schenectady, NY Lines: 57 In-reply-to: ccc_ldo@waikato.ac.nz's message of 17 Aug 90 00:15:54 GMT In article <1204.26c2fb48@waikato.ac.nz> ccc_ldo@waikato.ac.nz (Lawrence D'Oliveiro, Waikato University) writes: > In other words, I don't think protected mode is worth it. I disagree. In article <1252.26cbdffa@waikato.ac.nz> ccc_ldo@waikato.ac.nz (Lawrence D'Oliveiro, Waikato University) writes: > Mark has got it right, and Brandon [and Bruce] hasn't. My point was that, > whether these things are done in user-mode code or not, they can > still make the system unusable. A hook that allows replacement of the > system text-drawing routines can, if misused, turn much of the display > into garbage; a screen-saver hook can be used to destroy the display > completely. And so on. > Whether such behaviour is technically a "crash" or not is > irrelevant. The end result to the user is pretty much the same. You should realize that the "protection" in not "user" vs. "kernal". There are three levels of protection in most protected systems I use: 1) Kernal Protection 2) Window Manager Protection 3) Application Protection Given a stable OS and a stable window manager, no application should cause either the system or the window sessions to crash. If it does crash, then the software is immature. Changing the window environment can crash the session but not the OS. This is why such modifications are left to experts and commercial companies. INITs are changes to the window manager. They are a big headache today, and will continue to be a headache with a protected MacOS, because it is changing protected code. In that respect, Lawrence, you are correct. However, and this is the FIRST point, most of the Mac software today does not require modifications to the "common" toolkit. Assuming the Mac user has a very stable collection of INITs and CDEVs, the protected Mac should *never* crash. The SECOND point is: Not all applications require running in protected mode. While AfterDark/MacOS currently does, some windows systems do not require special privileges to execute a screen saver, or any other application you describe. It is even possible to kill your window manager, start up a different window manager with a completely different look and feel, and continue *without* interrupting the applications that are running. -- Bruce G. Barnett barnett@crd.ge.com uunet!crdgw1!barnett