On Thu, Apr 19, 2001 at 07:07:23AM +0100, Georges Heinesch wrote:

> What does the error message in <subject> mean

The 2 byte minus one bit buffer provided by the Amiga serial hardware did
overflow.

> and how can I avoid it.

> It happens during ftp download on my A3000, especially when moving the
> mouse with screenblanker or when moving windows around quickly while
> download is in progress.

What is the disk controller you are using?

> It's an A3000, ser0 is the internal serial prot (modem is connected),
> /netbsd is 1.5.
> 
> Any ideas?

Without knowing your full configuration:

- make sure both modem and PPP and cable in between know about hardware 
  handshake (crtsdts). Read "man pppd" and your modem manual about this.
  Look at the modem control lights to verify that the computer really does
  switch rts off, and that the rx data really DO stop to come in in this case.

- if this doesn't help, use options LEV6_DEFER in your kernel configuration.

- if this still doesn't help, increasing SERIBUF_SIZE might slightly decrease
  the overflow rate a bit.

- overall, you should operate the serial-modem connection at the slowest
  speed possible. That is, do NOT use V42bis or MNP5 with your modem; use
  PPP compression instead, and use the slowest serial speed that is slightly
  above your modem bitrate (e.g., for 28800 and 33600 use 38400). Commodore
  did specify the port for 57600 bps maximum, less DOES help a lot.

- if you have a disk controller that does LARGE dma transfers beyond what
  Commodore specified as maximum allowable without being interuptible by
  the CPU, tough luck. We did our best to limit DMA transfers and corresponding
  68040/68060 cache flushes in the NetBSD drivers if ser0 is used, but you
  might be forced to buy a serial port with a deeper fifo.

Regards,
	-is