Date: Sat, 7 Dec 1996 14:23:43 +1100 From: Bruce Evans <bde@zeta.org.au> To: grog@lemis.de, phk@critter.tfs.com Cc: FreeBSD-current@freebsd.org Subject: Re: Problems with PLIP driver? Message-ID: <199612070323.OAA13164@godzilla.zeta.org.au>
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>>1. There seem to be an abnormal number of errors on the line. In the >> following, freebie is my FreeBSD machine, and papillon is the >> laptop: > >Well, if there is a significant speed difference between the machines, >you will have a problem. `speed' probably means the speed of the parallel port bus interface. I haven't noticed any problems for connections between a P5/133 and a 486/33, but I only ran PLIP for 10 minutes to test it. The P5's ISA i/o is just as slow as the 486/33's. >>4. These problems seem to affect the Ethernet link (ep0) as well. >The problem is that your speed is probably around 70Kbyte/sec, that >means that the cpus are running for 22 msec with irqs disabled. This also loses one or two clock ticks. I haven't noticed any problems with the splhigh()s replaced by splimp()s. >It works sufficiently well that it is usable, but it is impossible >to get it to really work well and preserve a decent transfer-rate. Both together, that is. The old version of Linux PLIP that I'm familiar with does extra i/o's for debouncing. It was about twice as slow as FreeBSD PLIP (due to about twice as many i/o's). It could be made much more reliable by doing a complete handshake. This would also allow it to run reliably with interrupts enabled. Then it might be another 5 times slower. OTOH, modern enhanced parallel ports can go much faster. Bruce
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