Date   : Sun, 08 Feb 2004 20:35:46 +0000
From   : Jules Richardson <julesrichardsonuk@...>
Subject: Re: Tube ULAs

Hiyas,

> 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.

Silly one, but does the 286 board have a fuse on it (as the 6502 copro
cards do)?? There may be other voltage regulation on there too for the
memory which is worth a check... 

Any chance of the photo of the board? Never seen a 286 one.

> I'm not used to things just breaking. There must be either a logical 
> step missing, or a failed component.

well double-check cabling and power supply lines for starters. Re-seat
any socketed chips. Check power supply voltages.
  
>  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? 

Far as I know it's dedicated to the particular 2nd processor and not
independant :(

> 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,

Or a code for 512kbit devices maybe??

>  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).

Oh gawd, if that's the sort of socket I'm thinking of, leave it well
alone. Those things are a pig to sort out once you take the IC out,
without bending pins, breaking contact pads on the IC etc. (grrr!)

> 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 ;)

Well if it isn't the ULA, and the ROMs aren't toast, then anything else
can be fixed...

Pull the roms on it and back them up before you cook them :-)

> 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 ;)

I'm still missing a BBC 32016 copro board (as opposed to the 4MB one in
the ACW) and the 286 board like yours (although was it ever offered as a
BBC copro, or only in the ABC machines?). Oh, there was an ex-Acorn guy
on the classiccmp list a while back who'd built a 6809 copro back in his
day... don't think it ever made it out of the lab though...
  
cheers

Jules