Date : Sun, 08 Feb 2004 19:27:06 +0000
From : Richard Kilpatrick <oldcomputers@...>
Subject: Tube ULAs
I'm putting way too much mental effort into this...
Tube. Specifically, the 286 Tube in the ABC-310.
It booted once - only once, seemingly - when I first powered up the
machine. Initially, when powered up the 310 would come up like so:
Acorn business computer
Acorn ADFS
Language?
And didn't accept any keyboard input. Switching to Tube resulted in a
cursor. Stripping the machine of 1MHz bus devices, and doing
/something/ got the Tube up, but I can't remember what. Now I've traced
the monitor problem to the cable (doh!), I still have the flaky I/O
board (no sound - stick the BOS ROM into my ACW and it boots normally
with Acorn business computer etc, and beeps). I don't /think/ it's a
volume control/speaker issue as turning the control makes the speaker
crackle, and removing the control and placing a shunt on the
appropriate pins results in still no sound. I desperately need proper
ABC/ACW DNFS, ADFS, Language (standard BBC B+) and B.Ed ROMs.
I have connected the 286 board (powered by the ABC) to a BBC B+ 128K
which normally has a Z80 co pro attached. Again, nothing; regardless of
the position of the Tube switch on the ABC keyboard, I get the cursor
and nothing else. BBC B+ operation (Tube switch 'off' (power still to
Tube I presmue) and ctrl-break results in the usual B+ 128K etc.
I'm not used to things just breaking. There must be either a logical
step missing, or a failed component. My gut feeling would suggest that
the Tube ULA, if anything, is the most likely candidate for flaking
out. Is the Tube ULA a standard component regardless of CPU, or is it
dedicated to the second processor concerned? I ask because the one on
the ACW is different. I haven't checked the Z80. The ROMs on the 286
board - at least one of them - have labels dating from 1986 and stating
M512, which implies Master 512 code, but the board is assuredly 286
based and contains a 286 CPU (not PLCC as I mistakenly stated
elsewhere, but a surface-resting type held down by the heatsink).
What options are there for testing the Tube? Historically, this is
apparently a very rare bit of Acorn hardware and the idea that it's
broken - in fact, more the fact that when I was given it the assumption
was that it may or may not work, but I have managed at least once to
get a proper 286 startup) - is rather upsetting ;)
Oh, and I got an 80186 on eBay for, annoyingly, only a quid less than
CJE sell them for. I hope it works :/. That just leaves an ARM
development board and a 6502 wedge, and I should have all the Acorn
co-processors. No doubt I'll find one lying around somewhere ;)
Richard
--
Richard Kilpatrick
Older than most of his computers, but not by enough to know better.
Acorn: '82 to '98. Atari: '79-84. Apple: '84-04 (no Apple //, for
shame!).
http://www.dmc12.demon.co.uk/retrotech/