Re: Apple //e as serial terminal

[supertimer@aol.com (Supertimer)]

CUTblakeney@home.com (Jeff Blakeney) wrote:

>kragen@dnaco.net (Kragen Sitaker) wrote:
>
>>Louis Cornelio has kindly offered to sell me a Super Serial Card; I
>>suspect that should be quite sufficient.  (I am given to understand
>>that the //e occasionally drops characters even at 19200 bps, due to
>>missed interrupts; if this is true, faster wires won't buy me
>>anything.)
>
>If the IIe is unenhanced then you will most likely drop characters at
>19,200 bps, especially if the data is scrolling the text display.
>However, if the IIe is enhanced, the chances of dropped characters are
>much less.  If you accellerate your IIe and/or add a fast hard drive
>for downloading to, you will probably get even less dropped
>characters.

This is a common misconception.  I've used ProTERM
on a IIe with a Super Serial Card before and I know why
this misconception exists.  Early Super Serial Cards
have a faulty 6551 serial chip that is responsible for the
character loss.  It has nothing to do with the speed of
the computer.  Even if you plug the SSC with the faulty
chip into the fastest TWGS or Zip GS accelerated
system, you will not fix the character loss.

However, change the 6551 and the problem magically
disappears.  An Apple IIe, plain unaccelerated, will run
a 14.4k modem without losing a single character.

>Also, the Super Serial Card has a problem with hardware handshaking
>where it will cut off a character partway through transmitting it if
>the handshaking line tells it to stop sending.  This can be fixed but
>I don't remember the details.  I know adding a TurboASB to the Super
>Serial Card fixed this problem but I don't know if any are still
>available.
>
>I think that covers it.  If anyone has anything to add or correct,
>feel free.  :-)

The TurboASB itself does not fix the problem, but it
was sold with an optional 6551 replacement chip that
fixed the problem.