Date: Tue, 24 Oct 1995 14:44:10 -0400 From: dennis@etinc.com (dennis) To: Bruce Evans <bde@zeta.org.au> Cc: hackers@freebsd.org Subject: Re: Async utilization..... Message-ID: <199510241844.OAA00819@etinc.com>
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>>>How much less efficient? For logins, even a local ethernet is only a few >>>times more efficient than 115200 bps async through a 16450. This is >>>mostly because the pty implementation is poor. > >>Your numbers, like unix utilization >>and timing numbers, are garbage. Set up a controlled test where you know the >>answer >>and the numbers won't be close. > >FreeBSD isn't unix. The sum of the user, system and interrupt times is >accurate to within 5usec * (number of context switches) under FreeBSD, >but since the interrupt time is not available through any syscall and >my tests involve a lot of interrupts, I just used the real time, which >is accurate to about 1 part in 1000 here. > Its not a real measurement, so you can't use it. Period. Figure out the processing requirement for handling one average frame size of bytes with a 16450 with 8-bit I/O cycles and loads of interrupts, add 20% and compare it to a single interrupt and one 16-bit bus transfer per frame. It doesn't take a rocket scientist to know there's a signficant difference in processing requirements. Dennis ---------------------------------------------------------------------------- Emerging Technologies, Inc. http://www.etinc.com Synchronous Communications Cards and Routers For Discriminating Tastes. 56k to T1 and beyond. Frame Relay, PPP, HDLC, and X.25
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