Re: How to avoid serial port buffer overruns?

From: Raphael Hertzog
Date: Wed Aug 16 2006 - 10:55:33 EST

On Wed, 16 Aug 2006, Lennart Sorensen wrote:
> In my experience, the way to avoid overruns on a serial port was to use
> a buffered serial port UART (such as a 16550A for example). I remember
> my 486 wasn't reliable about 19200 or 38400 (depending on how busy the
> cpu was) when using an 8250. Using a 16550A based card and I could do
> 115200 without any issues since the UART had a 16 byte buffer to help
> out the system. Unless your 386 has an add in card for the serial port,
> it almost certainly has a very crappy UART and it would be very hard to
> make it work reliably at higher speeds.

I forgot to mention the kind of UART in my mail but it is a 16650A (and
configured as such and detected as such) and I have overruns nevertheless.

bash-2.05a# cat /proc/tty/driver/serial
serinfo:1.0 driver revision:
0: uart:16550A port:000003F8 irq:4 tx:31 rx:7 RTS|CTS|DTR|DSR
1: uart:16550A port:000002F8 irq:3 tx:24 rx:7 RTS|CTS|DTR|DSR

(here there's no overrun but I almost didn't use the serial port since
last reboot)

Raphaël Hertzog

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