From: jbradford@dial.pipex.com
To: linux-kernel@vger.kernel.org
Subject: 2.5.x and 8250 UART problems
Date: Sat, 5 Oct 2002 16:05:31 +0100 [thread overview]
Message-ID: <200210051505.g95F5Vvd000419@darkstar.example.net> (raw)
I've noticed that 8250 UART based serial port performance is poorer in 2.5.x than 2.4.x and 2.2.x, on a couple of my machines.
The 486 SX-20 with 4 MB RAM, running 2.2.21 reliably achieves about 650 BPS download from another machine, with the port runnnig at 9600 bps. With 2.5.40, many characters are lost at 9600, making, e.g. a ZModem transfer retry for almost every block.
A 486 SX-25 with 8 MB RAM, running 2.4.19 manages about 950 BPS reliably with the port set at 9600 bps. With 2.5.40, there are again a lot of lost characters.
I know these are ancient machines, with rediculously low amounts of memory, but surely 9600 bps should be reliable, even if performance drops to 600-700 BPS, or even lower.
I originally thought that the new kernel was using up memory that was previously available to be used as a buffer, and that extra hard disk access was causing the lost characters, but this doesn't seem to be the case.
John.
next reply other threads:[~2002-10-05 14:51 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2002-10-05 15:05 jbradford [this message]
-- strict thread matches above, loose matches on Subject: below --
2002-10-05 15:06 2.5.x and 8250 UART problems jbradford
2002-10-05 15:07 ` bert hubert
2002-10-05 15:18 ` jbradford
2002-10-05 19:59 ` Russell King
2002-10-05 21:12 ` jbradford
2002-10-05 19:43 Hell.Surfers
2002-10-05 20:01 ` jbradford
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