zmodem file transfer problems

[Alex Prengel]

Not sure this is the right group for this, but it was the closest I could find.
I am having problems sending files from a UNIX mainframe to my PC using zmodem
(I have used it extensively in PC to PC transfers and found it fast, reliable
and efficient). When I initiate the transfer from the mainframe (sz foo.bar)
and start the download on the PC end, the transfer begins but invariably starts
to generate errors (typically ZERPOS header, but also CRC ERROR and various
others). The errors start at a very consistent byte count (about 5K as I recall)
and then repeat frequently (about every 4 to 10K, though the interval is not
perfectly regular). Although zmodem will retransmit until the file gets through,
the transfer is much too slow, making it utterly impractical for large files.
The problem seems to be independent of phone lines, modem, baud rate etc. and
transfers from the PC to the mainframe work fine. I suspect that the problem
might have something to do with timesharing on the mainframe and vaguely recall
seeing a message somewhere to this effect, along with a suggested cure which I
do not recall. In case it matters, the mainframe is an HP 9000/850 running HP-UX
3.1 (very similar to system V). Any ideas for a cure would be appreciated! I
know there could be many other factors at issue and am mostly wondering if this
rings any bells.   Alex Prengel     alexp at chaos.cs.brandeis.edu