🚀 go-pugleaf

in article <9891@netnews.upenn.edu>, ranjit@eniac.seas.upenn.edu (Ranjit Bhatnagar) says:

> 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.

> 	* 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.  

You need about 2 Amps per slot, plus an additional 2 per box, if you're
following the specifications.  We say you get 2 Amps in any given slot,
but one board (presumably the one with "all that memory" on it can really
draw up to 4 and still be safe).  You need bus drivers 'ala "backplane
example" from the A1000 "Schematics and Expansion Specifications", or based
on the German A2000 design in "A500/A2000 Technical Reference Manual", 
with corrections.

>		I'd hope to be able to plug 2000-style memory and hard disk 
>		cards in it.  This SEEMS like it should be easy, so what am 
>		I missing?

It really isn't going to be very difficult.  There's no reason your 
Zorro II backplane connected to an A1000 or A500 shouldn't be able to
run most (if not all) cards, providing your backplane design is sound.

> 		What's a limit on the number of slots I can have?  

The limit you're most likely to run in to is the number of slots you
can serve by your DMA arbiter.  From a physical point of view, the
existing specs will have no trouble with 6 or fewer slots, though the
actual bus buffer implementation will set the real achieveable number.

>		How do I avoid timing problems and such?  

Look at the "B2000" design in the "A500/A2000 Technical Reference Manual"
and try to emulate that.  The maximum delay through the BUSTER chip is
speced at 40ns for non-clocked outputs.

> And where can I get a QUIET fan to put in the box?

I wonder if anyone at Commodore would know this -- I certainly don't.

> 	* 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.
> 		What DOES make a 32-bit card cost so much more than
> 		a 16-bit card, after you factor out the memory chips
> 		themselves?  And are 120 ns chips fast enough?

The actual interface available must be based on what Ronin presents on
their memory connector.  One obvious explanation for the extra cost of
such a board is "we're the only ones who make it".  If you're considering
building a 32 bit add-on, I'd suggest you get information on the Ronin,
GVP, CSA, and possibly other daughterboard hookups before designing the
card.  Even if you can't come up with a 1-board-fits-all design, you 
may be able to offer the same design with different connectors.

The speed of the chips you need is completely dependent on what you're
trying to do with the system.  You could build a board with 120ns DRAMs
that goes faster than normal A2000 RAM boards, but it's likely that
someone else will build one with 100ns DRAMs, which could beat the best
120ns design by a wait state.  	

> 		Would a hand-drawn pc-board be far too noisy for
> 		such an application anyway?  (Well, drawn in MacDraw
> 		anyway.)  Could the LUCAS design be easily adapted?

Nothing's inherently wrong with hand-drawn boards, if you're using a
CAD program of some kind, though you may have to manually follow 
design rules to get a reproducable board.  LUCAS looks like may have 
problems with other add-on devices.

> 	* A memory card - 32-bit or 16-bit - that would take SIMMs.  Sometimes
> 		those are cheaper.  

SIMMs are always more expensive than DIP or ZIP parts, by 20-50%.

> 	- Ranjit

-- 
Dave Haynie  "The 32 Bit Guy"     Commodore-Amiga  "The Crew That Never Rests"
   {uunet|pyramid|rutgers}!cbmvax!daveh      PLINK: D-DAVE H     BIX: hazy
              Amiga -- It's not just a job, it's an obsession