retr0brite not so right?

[Tony Duell]

> 
> On 02/08/10 19:36, Tony Duell wrote:
> > Even if I had to spend it on classic computers, the Apple 1 would not be
> > high up the list :-).
> 
> Agreed. As I've said, I'd rather like a SYM-1, KIM-1 or AIM-65. But 
> given that I've talked to a couple of people who said "yeah, I've got 
> loads of those in a warehouse, you can have one" and then dropped off 
> the face of the earth... I'm not hopeful.

Als I know the feeling. I've missed out on 3 HP1000s and an Acorn A680 
due to similar occurances. Oh well, life goes on...

> 
> Actually at this point I'd settle for getting my Jupiter Ace motherboard 
> back from Lee Davison. Again, chance close to nil. Even getting a bare 
> Ace PCB or a broken Ace to fix would be nice... I'd build up the bare 

Alas I only have one Ace, and I am keeping it :-). 

> PCB on the grounds that:
>    - It'll be a fun evening's work

Well, if you like fitting 1k resisotrs... In case you don;t know, the Ace 
has a vile 'myltiplexer' circuit consisting of a totem pole TTL output 
(say from a counter) warkened by having a 1k resistor in series 
contending with a 3-state output (say on an address buffer). That's how 
it allows both the video counter chain and the CPU to access video RAM.

The Ace claimed ot hgave 3K of RAM. While there are, indeed, 6 off 2114s 
onthe PCB,it's 1K of program/data RAM, 1K of video RAM, and 1K of 
character generator (there is no character generator ROM, the character 
generator RAM is loaded from the system ROM at power-up). Calling that a 
3L machine is somewhat dishonest...


>    - I know other people have bare PCBs and that they're not "one-off" 
> rare (AIUI a box of them was sold off when Jupiter Cantab went bust)

As I understood it, the stuff all went to a company called 'Boldfield 
Limited Computing',sho then sold it on (including complete, working Aces, 
that's where mine came from). A bit later, the remains were sold off at 
low prices. I sitll have a few games tapes somewhere. What I don't have 
is a bare PCB...

>    - As a bare board, it's as useful and as entertaining as a brick. 
> Build it up and it becomes a whole lot more interesting.

Err, of course. What else would you do with a bare Ace PCB?

> 
> > Err, the Apple 1 is a single-board machine :-)
> 
> Yes, but not the sort of machine I was thinking of (a "microcomputer 
> trainer" type thing)

I actually wonder what the real difference is...

> 
> > Hmm, we will ahve to agree to disagree, I think. I regard the Apple ][ as
> > one of the worst designs ever because it's such a minimal parts count
> > (IMHO a few more chips would ahve made it a lot better).
> 
> In some ways it is a completely evil design. Reverse engineering it is 
> diabolically hard, and I think some parts of the design must have been 
> conceived by a madman or a masochist. But getting the parts count down 
> that far? Cool.

No, I disagree. I have never been a great lover of minimal parts count 
designs. For me, the more hardware. the merrier :-)

> 
>  > But I feel the
> > BBC Micro is one of the best (if not _the_ best) 8 bitters. A very
> > elegant design...
> 
> The BBC is a lovely design. From an expandability point of view alone 
> it's something that -- even today -- is worth keeping on or near an 
> electronics workbench with a User-Port-to-breadboard cable. And if you 
> need a few more I/Os, there's always the 1MHz Bus.

Why do you think I have an ACW (== BBC B+ with 32016 coprocesosr, colour 
monitor, hard and floppy drives, all in one box) to hand? 

> 
> They make terrific logic pattern generators, the BASIC has full floating 
> point and a good range of math operators (I don't have a full list to 
> hand, but IIRC it at least has sine, cosine and tangent, and possible 
> arc-tangent as well) and the machine itself is built like a Chieftain 

ATN is certainly there... I would have to grab the (excellent) user guide 
to look for all the others. But for what I do, the built-in assembler is 
more useufl, actually...

> tank. Plus if something goes wrong, it's all LSTTL or easily obtainable 
> parts (aside from a ULA or two and possibly the SAA5050).

Indeed... And schematics are trivial to get. It's a very nice machine to 
work on...

> 
> Well, as long as you had a supply of spare 100nF X2 capacitors for the 
> power supply filter. Those go pop at an alarming rate, and have a rotten 
> tendency of caking the innards of the machine with brown ichor when they do.

Ah, the anitsocial capacitor problem. I've never seen it in a Beeb (but 
then the Beeb I use most is the ACW whiohc has a totaly different PSU), 
but I've seen it often enough in other machines. I rememebr when I was 
sorting out myu HP981, I left the monitor on and poweed down the CPU box 
to correct something. A few minotues later (by chance, as it turned out), 
the monitor went bang and emitted magic smoke. My instnat thought was a 
problem in the horizontal output stage. I powered down at once and 
removed the casing (non-trivial on that monitor...) and was relieved to 
find the only fault was that one of the filter capacitors had exploded 
(metalised foil hanging out of the side). Of course I replaced the lot...

-tony