Date: Wed, 13 Mar 1996 09:01:31 +1100 From: Bruce Evans <bde@zeta.org.au> To: bugs@FreeBSD.org, tedm%toybox@agora.rdrop.com Subject: Re: sio.c and pppd problem Message-ID: <199603122201.JAA07763@godzilla.zeta.org.au>
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>486/33 8MB RAM >Trident VGA (garden variety VGA card) >integrated serial/parallel/IDE controller cards, no-name clones using 8250 >uarts (non-buffered) >Intel EtherExpress16 network cards >Anyway, when I first set up the connection, I was running the ports at 9600bps >because I knew that without a buffered port card I wasn't going to get any more >throughput. ... A 486/33 can handle the peak loads from about 2 * 115200 bps unbuffered ports or about 8 * 115200 bps buffered ports. >The broken buffered combo cards work fine under OS/2, Windoze, etc. They just >don't seem to work under FreeBSD. Oh, it LOOKS like they work, at least if you >run cu they seem to work, but pppd WON'T work at all with them! There seem to be a lot of 16550 incompatibles around now :-(. >The following is what is on the bad card: >Winbond model W83777, FCC Identification ID2-W837787AA >There are 2 large chips on the card, they are marked: >Winbond W83787F and W83758F >I was able to get it running with the following cards: >card1) Kowell model KW-557 >The chip on this is: >SMC >FDC37C666GT >A9444-B247 >6J74183-2 SMC had a fifo bug, but it was fixed in software about a year ago and I suppose the h/w is better now. >card2) UMC something-or-other. (sorry, if you really want the ID#'s I get >them, but I didn't write them down) I'm trying to find workarounds for sio and floppy bugs in my UMC 8669F which is on rev 2.4 of the popular ASUS P55TP4XE motherboard. I don't know if the bugs occur in all 8669F's. The FDC sometimes interrupts early. This happens to cause long busy-waits, timeouts, failed retries and eventually data loss under FreeBSD-current. The UART always loses sync if the speed is set or the fifo enable bit is changed while data is arriving. The problem is most noticable for applications that set the speed a lot, e.g., uucp. I haven't noticed many problems with ppp or slip. >etc, etc. Also, the kernel does NOT emit overflow messages, and I DID change >sio.c to raise the buffer size mentioned in a hardware FAQ message on >www.freebsd.org. Also, YES the kernel thinks the broken cards are 16550A >cards. The only evidence of the UMC bug is garbage data. >One last thing I discovered with the SMC serial port card, is that if I set the >port speed to 57600 it sometimes locks up the machine. This is probably >because 57600 is too ambitious a speed for a 486/33 Unix box. A 486/33 shouldn't lock up with less than about 5 _unbuffered_ ports at such a low speed. (5 ports * 2 directions * 5760 interrupts/second = 57600 interrupts/second * 20 usec/interrupt = 1.1152 seconds/second = impossible. In practice some of the interrupts will coalesce and 20 usec/interrupt is an overestimate so 5 ports might actually work.) Bruce
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