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Path: sserve!newshost.anu.edu.au!harbinger.cc.monash.edu.au!yarrina.connect.com.au!warrane.connect.com.au!kralizec.zeta.org.au!not-for-mail From: bde@kralizec.zeta.org.au (Bruce Evans) Newsgroups: comp.os.386bsd.development Subject: Re: FreeBSD 1.1G - SLIP performance problems Date: 2 May 1994 15:28:35 +1000 Organization: Kralizec Dialup Unix Sydney - +61-2-837-1183, v.32bis v.42bis Lines: 28 Message-ID: <2q2323$12g@kralizec.zeta.org.au> References: <2pqst6$g4s@opine.cs.umass.edu> <Cp15CK.qII@mozo.cc.purdue.edu> NNTP-Posting-Host: kralizec.zeta.org.au In article <Cp15CK.qII@mozo.cc.purdue.edu>, Ben Jackson <bj@kidd.vet.purdue.edu> wrote: >In article <2pqst6$g4s@opine.cs.umass.edu>, >Jim Doyle <doyle@cs.umass.edu> wrote: >I think the "one-way" nature of your problem is the key... > >>* The 386PC (386dx40) has a 16550A on the port used for the SLIP interface. > ^^^^^^ >> It is connected to the PCRoute box useing a hardwired null-modem >> SLIP link. The SLIP link ran at 38400 bps, I did not try 57600. > >The 16550A has a FIFO which helps prevent data loss at high transfer >rates. As I understand it, though, there is just *one* FIFO, and you >have to choose which way it buffers (input or output). No, there is one dedicated to input and one dedicated to output. Perhaps the input one is broken? 1.1-BETA finally uses the full capabilities of the output fifo, but the output direction is the one that works. >I don't think it would be unreasonable to estimate that the FreeBSD >box is getting 16x the interrupt traffic in the non-buffered direction. FreeBSD has efficient serial interrupt handling and would hardly notice 16x the receiver interrupt traffic at a low speed like 38400 (it would cost about 5% on a 386DX40). -- Bruce Evans bde@kralizec.zeta.org.au