Re: Apple IIgs <--> PC question

[Jonas Bevren <jbevren@yahoo.com>]

On 3 Feb 2000, Supertimer wrote:

> Date: 03 Feb 2000 07:44:38 GMT
> From: Supertimer <supertimer@aol.com>
> Newsgroups: comp.sys.apple2
> Subject: Re: Apple IIgs <--> PC question
> 
> Jonas Bevren <jbevren@yahoo.com> wrote:
> 
> >I'm guessing in the dark here, but since the IIGS's ports are mostly super
> >serial compatible, I"d say they act like 6551 ACIAs at the appropriate slot
> >I/O pages (uhg, been a while, I cant remember the addresses)..  Am I right?
> 
> Nooooo!  In fact, programs that try to treat the IIGS' serial ports as
> though they were Super Serial Card 6551 ACIAs (like ADT) fail
> miserably.

<duck, cringe, running for cover> =)

> The IIGS uses a Zilog serial chip, the same one used on most of
> the older Macs and PowerMacs before the USB revolution.  It is
> capable of 57.6k speed asynchronously for driving a modem or
> 230k speed synchronously for AppleTalk.

You know, I should have guessed that (duh, it DOES have appletalk an'
stuff)..  I know which chip you're talking about, I have it's data sheet
someplace around here. =)

> For null modem purposes, the IIGS can do 57.6k which is quite
> an improvement over a Super Serial Card.  If the other computer
> is a Mac, you'd want to use AppleTalk through the ports which
> will allow 230k speed.

A couple comments =).

If you remove the crystal from the super serial card, and replace it with
one that's twice the frequency, all data rates you select will be doubled in
reality.  i.e. to get 115k on your trusty super serial card, install a
2x-speed crystal, and select 57.6k.  I dont know how well apples handle a
flood of IRQs (or does the SSC use NMI?), but you dare not do that on a
stock c64 (where the modification originated, in the 6551-based swiftlink
cartridge).  A stock c-64 can hit 38400 without a sweat, a stock c-128
(which is blessed with 2mhz speed) can hit 115k with a slim enough serial
driver.  It's quite impressive in fact.  My rommate is connected to one of
my linux boxes via a 25-foot nullmodem cable, and uses 115k constantly with
his accelerated 128-in-a-tower.

Last, =) I thought appletalk was 280kbit SDLC, or is it tolerant of speeds
varying that far?  I hate to nit-pick, but people need to know the right
numbers (even me IF I'm wrong!) =)

Enough drivel for now =)

-Jonas