Re: IIc & 14.4 kb modems

[spector@vax2.concordia.ca (Mitchell Spector)]

In article John_L._Graham@adbbs.antioch.edu writes...
>
>I seem to recall hearing the Apple IIc had problems with high speed modems.
>This issue has come up again with one of our local users. Can someone fill me
>in on the details, and does it effect all three verisons of the IIc? 

	The serial port problem was only present in the original 
Apple IIc, or to be more specific those manufactured between April 
1984 to December 1984. That end date may vary by a month or so, I
have a IIc motherboard with a November 1984 production code yet it
has the updated part which qualify it as the "good" serial port
revision.

	You can easily identify whether you have the "good" or
"bad" Apple IIc serial ports. Open it up and have a look a the
motherboard, then search for location C-7 and examine the part
at this location.

- A 74LS161 black TTL chip = ["bad" part]
- A silver oscillator with MHz rating = ["good" part]

If you have the "bad" part, modems and other devices may not work
above 300 baud, although this varies with different brand and types
of modems. The TTL chip part causes the ports to be about 2-3% off
in terms of speed, the oscillator on later revision motherboards
fixed this. Apple discontinued the free upgrade about a year ago
so you'll either have to pay to have the upgrade done (good luck
explaining what an "Apple II" is to your local Apple dealer ;) or
do a motherboard/part swap yourself.

>Thanks!
> 
>John

Mitchell Spector
spector@vax2.concordia.ca