From: grr@cbmvax.commodore.com (George Robbins)
Newsgroups: comp.sys.amiga.hardware
Subject: Re: A4000 Hardware questions
Date: 14 Oct 92 04:29:20 GMT
Reply-To: grr@cbmvax.commodore.com (George Robbins)
Organization: Commodore, West Chester, PA

In article <1992Oct12.171657.14149@ecsvax.uncecs.edu> urjlew@ecsvax.uncecs.edu (Rostyk Lewyckyj) writes:
> In article <35768@cbmvax.commodore.com>, grr@cbmvax.commodore.com (George Robbins) writes:

> > The problem has little to do with the RS232 standard and more to do with
> > the printer port and floppy and IBM's wretched choice of using DB25's
> > for both serial and parallel ports.

> George, I can't understand how IBM's poor choice of using DB25 
> connectors for both serial and parallel ports has anything to do
> with whether the circuitry behind these ports is or is not protected
> on C= Amigas.

> C= could certainly have chosen to use the parallel type connector.
> They did not hesitate to choose a 23 pin (uncommon) connector 
> Don't pass the buck.

Actually, the choice of the 23-pin connectors was made at Amiga, before
Commodore "hardware engineering" had any particular input into the
design - I've never seen the benefit, when a standard DB15 pin connector
could have handled the essential signals.

Do you remember all the fuss when we changed the sex of the parallel
and serial port connectors from the A1000 to A500/A2000?  That was done
to conform to IBM/PC practice so that users could expect to pick up
something as simple as a sandard parallel printer or modem cable at
their corner Radio Shack or Computer store and have it work.

On the Commodore product I worked on before the Amiga, I lied, cheated
and stole to get the standard "Centronics" connector on there as the
Parallel port, becuase it was the "right" connector and would prevent
folks from getting the two confused.

Unfortuantly, with the Amiga and what we wanted to do in terms of the
A500 marketing channels, conformity with the PC standard was the ticket.

> > In the original A1000 design, the 8520's had their outputs directly
> > wired to the I/O connectors.  This isn't very rugged, but is the most
> > flexible as far as supporting both input and output, especially for
> > ad-hoc peripherals that use the parallel data lines for random bit
> > I/O control/status signals.
> > 
> > Theoretically, 8520's were cheap and easily replacable, but in the

> Whose theory and definitions are these? What is the current cost and
> availability of the 8520 chips? $.50-$1.00 from multiple sources?
> THe chips protecting the cia should be cheap and socketed. 
> CHeap in practice not just in theory.

Measured against the added cost of "protective" chips or components on
a bunch of I/O lines (count 'em), which will also be subject to ESD
failure.

You're free to disagree with the decision or assert that "bullet
proofing" is required, I merely point out that we have considered
these issues and made changes as we though neccessary.

-- 
George Robbins - now working for,     work:   to be avoided at all costs...
but no way officially representing:   uucp:   {uunet|pyramid|rutgers}!cbmvax!grr
Commodore, Engineering Department     domain: grr@cbmvax.commodore.com
Newsgroups: comp.sys.amiga.hardware