Odd RS232 problem

Daniel O'Connor doconnor at gsoft.com.au
Tue May 23 02:55:02 PDT 2006

On Saturday 13 May 2006 22:00, Holger Kipp wrote:
> First, make sure you have a dedicated IRQ for the card.
> Then, add options PUC_FASTINTR to your kernel config.

This is impossible :(
I can't change what the BIOS does, and rearranging the cards is not possible 
remotely :)

I would hope that 9600 baud wouldn't be *too* fast for a 2GHz CPU :(

> If you encounter silo overflows, you might need to increase
> cp4ticks in sio.c, eg
> - cp4ticks = speed / 10 / hz * 4;
> + cp4ticks = speed / 10 / hz * 40;
> and/or you might want to change hz from 1000 back to 100.

OK, I'll try it.

> Have you looked at the port speed and if it is changing or
> has different speeds on both ends? The card together with
> the modems were really trying very hard to get the data to
> the other side, and were very good at it, especially with
> smaller chunks (necessary for dialing and authentication).
> Problems then started with real traffic going over the line -
> and we didn't get any errors in messages...

It is a fixed speed device so I don't think this is the problem.

> My impression is that serial io irq-handling on 6.x needs
> some improvement (personal feeling: it is much worse then
> on 4.x).

Yes, I think the interrupt latency in 6.x is much higher.

Daniel O'Connor software and network engineer
for Genesis Software - http://www.gsoft.com.au
"The nice thing about standards is that there
are so many of them to choose from."
  -- Andrew Tanenbaum
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