Date   : Thu, 03 Sep 1998 12:46:37 +0100 (BST)
From   : Carlo CONCARI <concaric@...>
Subject: Introducing myself and some questions 

Hi,
my name is Carlo Concari, I'm 21 years old, I'm Italian and I study
Electronic Engineering at the University of Parma.
My first computer was an 'Olivetti Prodest PC 128 S', bought in mid 1988.
I've been using it, coding in Basic and ASM until 1992, when I bought a
386.
Then I almost forgot my old computer, until the beginning of 1998...
....when I got an Internet account at school, and rambling around the Net
I found
this wonderful site called 'The BBC Lives!'. Reading the tons of
documentation that I downloaded from this site I discovered that my old
'Olivetti Prodest PC 128 S' is indeed... an Acorn Master Compact!
With all the technical information available on 'The BBC Lives!' about the
internals of the BBC series microcomputers, I decided to write an emulator
for my old computer. Taking advantage of the fact that for my Electronic
Calculators exam I was supposed to write an ASM program for the IBM PC, I
wrote a 65SC12 emulator, that availed me a 30/30 (full mark).
The 65SC12 emulator was a good point to start from, and during my spare
time this summer vacation I have implemented some other hardware (System
VIA, keyboard, interrupts, EEPROM, and a minimal MODE 0), and after a
never ending debugging week (I won't write 2000 lines of ASM without
testing any of them anymore! :) I have finally seen the 'Olivetti MOS'
prompt coming out of my PC monitor.
This happened some days ago.
Currently I'm planning to translate my 65SC12 emulator from Italian into
English and to upload it on 'The BBC Lives!' as freeware, along with the
source code. I hope to do so in the next 2 weeks; after that I will work
to improve my Acorn Master Compact emulator to a decent level before my
Uni lessons start over... maybe I will upload the current version together
with the 65SC12 emulator if I can add some user interface.

Some words about my Acorn Master Compact emulator's current state.
It is completely written in 8086 assembly (real mode), and I am very
impressed of how fast and small an ASM program can be: it is less than
20KB, and on a 66 MHz 486 it runs at full speed; on my Cyrix 686 P150+ it
runs three times faster than the real thing (yes I know, as I implement a
better video routine and the missing hardware, speed will lower down, but
who cares?). All this goes beyond the best hopes I had when I started this
thing five months ago!
Currently I'm missing some technical information that I hope to find
joining this mailing list. Here are some questions:

How does the 6502 manage the NMI's? I mean, when it receives an NMI does
it ignore the NMI line until the next RTI instruction or what? (If it
doesn't do something like that, I thing it would hang in an infinite
loop).
Is the NMI line edge or level triggered?

Also I'm looking for some info about programming the 76489 sound chip and
some tech info about the WD1770/1772. I have a printed (Italian) copy of
the Reference Guide and the Master Advanced Reference Guide downloaded
from 'The BBC Lives!', but I can't find anything on them about sound and
disk.
Thanks in advance for your help and I hope I didn't bore you too much with
my rumblings.
                                                                          
                                                       Carlo.