Subj : Re: Pi4 to Pi5 migration To : The Natural Philosopher From : Ahem A Rivet's Shot Date : Mon Jun 17 2024 17:51:41 On Mon, 17 Jun 2024 17:02:37 +0100 The Natural Philosopher wrote: > Very hard to put a decent Unix on a 286 - Venix was the only one, I > recally. No memory management. XENIX was available for the 8086 and the 80286. Altos used to make a surprisingly usable XENIX machine with an 8086 main processor and a pair of Z80B IO processors (one for the serial ports, one for the tape and disc). They kept this basic architecture while upgrading processors (80286+2x8086, 80386+2*80186). The 80286 had a protected mode with memory management but did not supply any means to exit from it so the transition to kernel side unprotected mode had to be done by calling on the keyboard controller to reset the processor - code then checked a flag location for the value that said this wasn't a cold boot. > the 386 made porting unix pretty simple. SCO unix was extremely stable. It certainly did. > Wasn;'t that a Xenix evolution? Yes SCO bought XENIX from Microsoft, then when they switched to the SysVR4 codebase (AT&T pulled in everything they could from XENIX and BSD) they got to rename it to Unix. The earlier XENIX was also rock solid IME on PC or Altos hardware. -- Steve O'Hara-Smith Odds and Ends at http://www.sohara.org/ For forms of government let fools contest Whate're is best administered is best - Alexander Pope --- SoupGate-Win32 v1.05 * Origin: Agency HUB, Dunedin - New Zealand | Fido<>Usenet Gateway (3:770/3) .