Path: utzoo!attcan!uunet!lll-winken!ames!pasteur!ucbvax!PSUVM.BITNET!ART100
From: ART100@PSUVM.BITNET ("Andy Tefft  862-6728", 814)
Newsgroups: comp.sys.apple
Subject: Null modem file transfer
Message-ID: <8901091916.aa10622@SMOKE.BRL.MIL>
Date: 10 Jan 89 00:08:00 GMT
Sender: daemon@ucbvax.BERKELEY.EDU
Organization: The Internet
Lines: 31

I have had great success transferring files via null modem cable from my
//c to a friends IBM PC clone. I used 19200 baud, and the limit on the speed
I could really transfer files seemed to be only caused by disk read/write
delays. Wish I had had a ramdisk/hard drive on the clone.

I used both Zlink and Kermit 3.84 at 19200 baud. Kermit was quite a bit
slower for two reasons: It read the disk more often, and seemed to have
more overhead (I used Kermit protocal on Kermit and XMODEM on Zlink.
I also wish there were YMODEM on the clone at the time!). For a 30K
GIF file, throughput was about 6000-7000 baud (measured in actual data
bits/second, assuming 8-bit characters). Kermit was about half as fast.
It was quite interesting to watch!

By the way, what I used as a null modem cable was a "null modem adaptor"
from radio shack (Male db-25 on one end, female on the other). This connected
directly (well almost) to the back of the clone (needed a female-female
adaptor, too, but this was around because it was needed to hook up his
modem), and my regular //c modem cable was connected to the adaptor.
I was gonna make myself a null modem cable, but it would have cost me
$6 plus soldering plus some way to protect the wires (wasn't going to buy
hoods for those db-25's! at $2 apiece), and the adaptor was only $8 anyway.

if anyone wants wiring diagrams for a null modem cable, I believe I have
some. the basic idea of it is to switch all send-receive pairs (i.e.
SD of one end goes to where RD would be on the other end). It's a great
way to transfer files like GIF files and text files between computer brands/
disk formats. It was even convenient enough to take my //c over to the
friend's house that has the IBM, instead of just calling up and transferring
via modem.

Andy