5 May
2016
5 May
'16
2:55 p.m.
Thanks, Erik.
How do I remember this ca. 40 years later?
Well, while servicing these systems they would frequently stop with a "Memory Protect
Error" (various Operating Systems).
Guess what the intuitive action was: Replace the "Memory Protect Board" - which
n e v e r fixed the problem.
So digging into the technology it became clear, that the Memory Protect Board in these
cases had only fulfilled its duty: protect the memory below the fence register from some
other piece of hardware (usually a processor or DMA-board) running havoc in memory. That
learning stuck ...
Kind regards,
Gottfried
_____
Gottfried Specht | Gottfried at specht-online.com | +49 211 151695?+49 151 2911 2915
-----Urspr?ngliche Nachricht-----
Von: cctalk [mailto:cctalk-bounces at classiccmp.org] Im Auftrag von Erik Baigar
Gesendet: Donnerstag, 5. Mai 2016 10:36
An: General Discussion: On-Topic and Off-Topic Posts
Betreff: Re: AW: When did Memory- and IO Protection Emerge (Esp. in Minis)?
On Wed, 4 May 2016, Gottfried Specht wrote:
I'm not sure whether it qualifies for your full
list, but the HP2100A
(that came out in 1971) had a "Memory Protect" hardware that
Hi Gottfried,
thanks for the excellent answer - yes I think this is exactly what matches my
specification! Thanks.
It is really astonishing how many people know a lot on various machines which is really
great. I suspected that HP had something, too.
Fence Register: Set under program control; memory
below fence is protected.
This is a clever and somewhat outstanding feature - most others use protection on basis of
blocks ar abuse the virtual memory for the purpose ;-)
Best regards,
Erik.
-----Urspr?ngliche Nachricht-----
Von: cctalk [mailto:cctalk-bounces at classiccmp.org] Im Auftrag von Erik
Baigar
Gesendet: Dienstag, 3. Mai 2016 17:53
An: cctalk at classiccmp.org
Betreff: When did Memory- and IO Protection Emerge (Esp. in Minis)?
Dear Experts,
during discussing the Rolms I came accross the following question:
What was the first (Minicomputer) architecture which offered
memory- and IO protection? I'd define the minimum requirements as:
- Existence of a superuser mode (Rolm calls this Executive mode)
- Existence of a user mode (With at least two users, Rolm offers 4)
- In superuser mode, IO and memory protection for each user can be
set up individually.
- Any access violation is trapped and handeled by superuser code.
- Of course commands for mode switching and setting up the
memory and IO ranges must exist.
I have got a real machine (Rolm 1602) having this implemented and dating from 1975. A
document on this "Access Protection Module" as Rolm calls it also is dated 1975.
It consists of a microcode module which realizes an extension of the 16 bit Nova
instruction set and an additinoal CPU module, taking care of the new modes and supervising
the IO- and memory accesses.
My question is not regarding virtual memory memory, but regarding protection (IO and
memory) to ensure capsulation of indivitual processes - not necessarily for multi user
environments but e.g.
for safety critical applications...
Probably OS/2 in 1987 was one of the first home computer OSes to support memory
protection (how about IO protection?), BSD on some Digital PDP-* was earlier (1977?) but
still after the 1602.
Any hints out there on other "Mini" architectures of that era having someting
similar?
Erik.