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- Subject: Re: Simplest program (1+1=2), CP/M and UpLua Project
- From: Fernando Jefferson <fjefferson@...>
- Date: Sun, 03 Nov 2019 16:55:31 -0200
Really, happy days ...
Did you said 256K? Lucky you ... We started with 32K and then 64K.
My master's degree project was to develop part of a node for REDPUC, an
experimental pre-Ethernet packet network.
We've developed it all from scratch: hardware, BIOS, multiprogramming
core and OSI protocol up to level 2.
With a huge team of one person (Me) ...
Em 2019-11-02 19:16, Tim Hill escreveu:
On Oct 31, 2019, at 6:58 PM, Fernando Jefferson
At PUC-Rio we did reverse-engineering of CP/M 80, obtained a source
file, first in assembler and then in "C". And even we´ve developed
a CP/M 86, with the providential help of Roberto Ierusalimschy (my
colleague in the master's degree), who developed a genial
interpreter for the 8085 CPU, running on the Intel 8086. Mapping
registradors from one CPU to another!
Ah good memories. I did a similar thing for a commercial computer
system way back, which allowed us to move to x86 systems but still run
all the 8-bit 8080 software(quite a lot at the time) on the newer
machines. It really wasn’t that difficult as the x86 used a similar
model for flags, so it was really a matter of decoding the 8080
instruction and then mapping it to the equivalent 8086 instruction(s).
As I recall, the emulator run at about the same speed as the real
hardware. The OS mapping was equally simple, as CP/M and CP/M 86
mapped 1:1 for OS calls.
Happy days .. when 256K was a LOT of RAM :)
CCE-PUC-Rio - Professor
Projeto UpLua - Coordenador