[TUHS] Apple IIe Unix?
cowan at ccil.org
Sat Nov 28 02:22:00 AEST 2020
On Fri, Nov 27, 2020 at 6:55 AM Noel Chiappa <jnc at mercury.lcs.mit.edu>
> The thing that takes special hardware is _protecting_ one task from a bug
> another - a bug which could trash the first tasks's (or the system's!)
> memory. One has to have memory management of some kind to do that.
Actually, a modified version of the * approach will also work. When
switching processes, swap the whole process out to your fastest device (on
* this was a single write to the drum) and swap in the new process. *
hardware had a bounds register, so it was only necessary to swap out enough
of the previous process to fit the smaller process in. So after a while,
core started to look like an onion, with the current process at the bottom
and pieces of larger non-current processes above that.
(I thought that * was MIT CTSS, but I can't confirm that.)
As for interrupts, the stock 2e has both IRQ and NMI lines. Erann Gat aka
Ron Garret explains in <
how to make an external clock and hook it to the NMI pin for 25 cents in
1981 dollars (about $1.67 today; h/t measuringworth.com).
John Cowan http://vrici.lojban.org/~cowan cowan at ccil.org
A mosquito cried out in his pain,
"A chemist has poisoned my brain!"
The cause of his sorrow / Was para-dichloro-
Diphenyltrichloroethane. (aka DDT)
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