Date: Wed, 8 Mar 2000 17:06:11 +1100 (EST) From: Bruce Evans <bde@zeta.org.au> To: Archie Cobbs <archie@whistle.com> Cc: Brendan Kosowski <brendan@bmk.com.au>, FreeBSD Networking <freebsd-net@FreeBSD.ORG> Subject: Re: pppd / com-port question Message-ID: <Pine.BSF.4.21.0003081650210.621-100000@alphplex.bde.org> In-Reply-To: <200003071857.KAA42008@bubba.whistle.com>
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On Tue, 7 Mar 2000, Archie Cobbs wrote: > Brendan Kosowski writes: > > What is the maximum speed I can run pppd at on a FreeBSD box with 16550A > > com ports ??? > > 16550A supports up to 115Kbps The 16550A supports up to 1.5Mbps. Most serial cards only suuport up to 115.2Kbps, but ones supporting 960Kbps are fairly easy to find. FreeBSD only supports up to 115.2Kbps properly. Programs using the crufty sgttyb compatibility interface will mess up higher speeds. The sio driver only supports up to 115.2Kbps properly. It just gives the speed of the hardware clock divided by 16, and doesn't support setting of hardware clocks. You can sometimes set the hardware clock to a nonstandard value using jumpers on the serial card, and then sio will report the speed wrong by a factor of (nominal_clock_speed / clock_clock_speed). E.g., a speed of 115200 bps would be actually 961600 bps if the clock is jumpered to be 8 times as fast as usual. sio.c probably needs minor modifications to avoid silo overflows at 960Kbps (change the fifo trigger level from 14 to 8). sio probably has can't keep up with more than 1 or 2 ports at 960Kbps. Expect a CPU overhead of 50% per fully active port. Bruce To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-net" in the body of the message
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