--- Bill Pechter <pechter(a)pechter.dyndns.org> wrote: Mine has SysIII/UniPlus. Got all the docs and disks, too. My apologies for not being clearer... IIRC, there are two 68000 CPU chips in the box. One runs the OS, the other is part of the memory management system. Since the 68000 itself (not the 68010 and up) does not save enough information on a page fault trap to restart instructions, the way I was told the Perkin-Elmer worked was to have the other CPU kick in on a page fault, load the page, then somehow automagically get the main CPU to resume without loss of information, etc. Perhaps it holds off DTACK during a page fault, then releases it when the page is ready to go; I don't know any technical details and I never did anything with the kernel on it. I was just a user then an admin. The hairiest thing we ever did to the box was to replace a power supply and an HDA. This sort of gyration was obviated by the 68010 since it _did_ fully support virtual memory. Old Suns went that way, as did the NCR tower I have. I remember sticking in the '010 into my Amiga 1000 for the 5% performance gain that came from the two instruction cache/loop mode enhancement. Very few programs after AmigaDOS 1.2 used the now-supervisor-mode MOVEcc instructions and in any case, there was an OS patch to add a trap handler for that (but I digress wildly). We got the Perkin-Elmer because it was a) cheap b) 68000-based. I'm happy to have rescued it at the end of its useful life eight years ago. -ethan ===== Even though my old e-mail address is no longer going to vanish, please note my new public address: erd(a)iname.com The original webpage address is still going away. The permanent home is: http://penguincentral.com/ See http://ohio.voyager.net/ for details. __________________________________________________ Do You Yahoo!? Yahoo! Messenger - Talk while you surf! It's FREE. http://im.yahoo.com/