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From: ranjit@leguin.cis.upenn.edu (Ranjit Bhatnagar)
Newsgroups: comp.sys.amiga.tech
Subject: Re: Need advice on hardware projects
Message-ID: <10267@netnews.upenn.edu>
Date: 23 Apr 89 07:44:27 GMT
References: <9891@netnews.upenn.edu> <6622@cbmvax.UUCP> <7916@killer.Dallas.TX.US>
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Reply-To: ranjit@leguin.cis.upenn.edu.UUCP (Ranjit Bhatnagar)
Organization: University of Pennsylvania
Lines: 145

Thanks to Dave and Eric for their advice!  With a bit more help
like this, LUCES (a Little Ugly Cheap Expansion System) may show
up soon.

elg@killer.Dallas.TX.US (Eric Green) writes the > lines:
daveh@cbmvax.UUCP (Dave Haynie) says the >$ lines:
I wrote the >$> lines:

>$> I'm considering building one or more of the following hardware
>$> projects, for kicks and to save some dough.  
>$That's cool, and really shouldn't be any major design problem.

As it turns out, at the time I posted the original message,
I was under the impression that there wasn't much more to an
amiga card cage than 100 parallel wires and a buncha sockets.
I have no experience in designing bus arbitration circuitry,
and the ancient white hardware manual doesn't say enough to 
teach me.  But with someone else's electrical design (HINT!)
I could probably manage the layout and mechanical stuff.
>
>However, there may be some construction problems. I remember reading
>about noise nightmares with wire-wrapping on ancient S-100 busses
>using 2mhz 8080s, and similiarly with memory boards, so will
>definitely have to be a pc board. Do you have the facilities? If not,
>prototyping services can get expensive real quick (i.e., forget about
>saving some dough).

What about a board laid out in MacDraw or some similar CAD program,
and then optically printed or silk screened?  I can do that in my
basement... except for drilling the holes.  How practical is it
to print a board on perforated PC-board?  Would have to make the
traces extra wide so they're not interrupted by holes, but it would
save tremendous amounts of time not to have to drill.

Silk-screening is very cheap and fast, so if there is a way
to avoid making your own holes, I think it could make it worthwhile
to avoid the professionals for runs of a hundred or less...
(and I was only thinking of ONE!)
>
>$> 	* A zorro-II card cage for the 1000 
>$> 		I figure I need a case, a real smooth power supply,
>$> 		and about a zillion bus drivers.  
>
>This would be a VERY good project. Current Zorro-II card cages only
>have 2 or 3 slots, and are somewhat pricy (i.e., >$175). I suspect
>that most of that's because of the power supply and case -- a
>commercial outfit cannot rely on cheap surplus power supplies and
>cases. You can. 

Yeah - I figured about 50 bucks worth of parts altogether.

>   I just asked my brother what it'd cost to get quantity three from a
>prototyping service. He said it'd be probably about $40/board plus a
>setup charge of maybe $100. Going quantity 100 would probably bring
>the blank PCB cost below $10, but the question of what to do with the
>other 99 arises ;-). 

Well, that's pretty cheap.  If something like this took off like Lucas,
it would be worthwhile.

>$> And where can I get a QUIET fan to put in the box?
>I always wonder about people who insist on QUIET fans. The first time
>I turned on an Amiga 1000, I almost freaked, because I didn't hear the
>vigorous "whoosh" of most AT-clone fans. That "whoosh" is reassuring
>to me, because it means that my fan is still running and my equipment
>is still keeping cool. 

And it keeps ME awake at night.  Can't wait to dump the 2000 for a nice
peaceful 1000.  (OR move the 2000 into another room...)
 
>$> 	* A 32-bit memory card for the Ronin Hurricane 1000.
>$> 		I have no idea how complex a project this is - there must
>$> 		be SOME reason why an unpopulated 32-bit card costs
>$> 		over 500 bucks, but I'd love to avoid paying that.

I got nice answers about low volume and high startup costs, but
what I really was hoping for was design hints.  Is refresh circuitry
qualitatively different for such an application?  (Not that I know
anything about ordinary refresh circuitry - but I learn fast.) If one wanted
DMA, how would one do it?  Has anyone out there reverse-engineered
Ronin's memory connector, or would I have to plead with them for info?


Although I'm no longer in any hurry on this project, because I decided
to just buy a 2-meg SOTS box and put off the expansion and 32 bit memory
til later, I'll keep at it if other people seem enthusiastic and if I
can get help designing interface circuits.  No reason why this shouldn't
go the way of LUCAS - a nice, cheap design for all to share.

Some things to think about...

One can probably save money and get quicker results for quantities
under 100 or so boards by silk-screening them.  I've used silk-screen
only for fine-arts applications, but the application to pc design
is obvious.  A silk-screen kit costs about $40 in an art store; a
laser-printed design can be optically transferred to the screen in
about 3 hours; after that, one can turn out about 30 prints an hour
with registration precise to about 1/20th of an inch if one is careful.
(Important for doing 2-sided boards!)  Then dump all the prints in
acid and there you have it.  I still don't know how to handle the
holes, though... automated drill presses are a bit more expensive.
This technique is practical if there are no major objections to
printing on prepunched PC boards.

If there are people out there who are enthusiastic about such a
project AND know what they're doing (I only satisfy the first 
condition), I wouldn't mind if they did all the work, in the form
of a circuit design for the expansion controller and, optionally,
a layout.  I would be happy to turn the design into a layout and
turn out one or two or a dozen boards (once you've got the silk
mask, there's no reason to stop).

How about a system that sits above the 1000 or below the 500, just
by rotating it?  I like the subsystem idea because it saves desk
space.  Of course, a design that lies the cards on their sides
requires sideways-mounted daughterboards and brackets to keep the
cards from sagging.  Can hardcards safely be operated sideways?
Four slots in the 2000 take up about 3 inches of width, implying that
a four-slot sub/supersystem could be just 4 inches high or so,
and perhaps 6 inches wider than the length of a card to make room
for a power supply and/or a half-height floppy or hard disk.

Any objections to having the power supply in
a separate box?  That way it can be stowed on the floor to save
desk space, or on the desk to save floor space.  As Eric
pointed out, any old surplus power supply will do... there's
always 4 or 5 choices in the $20-30 range in the Computer Shopper.
What's the maximum power requirements one would expect for four
2000 cards and one 3 inch hard disk?

Should the expansion case have a pass-thru for any old SOTS boxes 
you might have sitting around?  Could this cause any electrical
problems?

Should the case be painted Commodore Tan (boring) or Pixar Speckled
(glamorous), or maybe black with brushed-chrome highlights and a
little green flourescent 7-segment display that tells you just how
much money you're spending...

	--ranjit


"Trespassers w"   ranjit@eniac.seas.upenn.edu	mailrus!eecae!netnews!eniac!...
	I'd be calling all the hotlines/I'd be missing all my deadlines
	I'd be standing in the breadlines/I'd be six feet underground