Markus Kilbinger <kilbi@rad.rwth-aachen.de> writes:

> 
>     Charles> Markus Kilbinger <kilbi@rad.rwth-aachen.de> writes:
> 
>     >>  Hmm, I tried the patch, but it didn't change anything
>     >> obviously. There are still lost chars on output decreasing
>     >> dramatically the final transmission rate even at a serial speed
>     >> down to 38400 baud.
> 
>     Charles> You're losing characters on *output*?  I've never heard
>     Charles> of this before.  What's on the other side?  Does it have
>     Charles> flow control enabled?
> 
> On the other side is a modem (max. 28800 baud) with enabled RTS/CTS
> flow control. E. g. trying to download files from this machine on this
> way (no matter using Zmodem or a PPP connection) leads to incorrect
> transmitted data packages every 6-8 kB. Turning down the transmission
> speed between this computer and the modem from 115200 to 38400 lowered
> the error rate, but didn't solve the problem. We also proved that with
> another modem and a null modem connected computer: Same behaviour. It
> seems like the reaction on the hardware handshake fails sometimes as
> the reason for this problem.
> 
> If it helps: At the beginning of this year there was a patch from
> Sommerfeld (formerly available on ftp.netbsd.org .../arch/i386 and
> some mirrors; I still have it ;-), but it's not (easily) applyable to
> -current sources) which solved the serial problem completely for us.

No; unfortunately, this doesn't help at all.  You haven't told me the
type of modems or what the receiver is.  And I'm not able to reproduce
any such problem here.

The patch you attribute to Bill Sommerfeld is just an earlier version
of the work by Onno and I.  If it works, it's only because you got
lucky; it has numerous serious bugs.