Return to BSD News archive
Path: euryale.cc.adfa.oz.au!newshost.carno.net.au!harbinger.cc.monash.edu.au!nntp.coast.net!fu-berlin.de!irz401!orion.sax.de!uriah.heep!news From: j@uriah.heep.sax.de (J Wunsch) Newsgroups: comp.unix.bsd.freebsd.misc Subject: Re: "fdc0: input ready timeout" Problem Date: 5 Sep 1996 06:55:44 GMT Organization: Private BSD site, Dresden Lines: 27 Message-ID: <50lthg$php@uriah.heep.sax.de> References: <3222B322.167EB0E7@cs.uni-sb.de> <50f1i6$hpb@nntp.ucs.ubc.ca> Reply-To: joerg_wunsch@uriah.heep.sax.de (Joerg Wunsch) NNTP-Posting-Host: localhost.heep.sax.de Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8bit X-Newsreader: knews 0.9.6 X-Phone: +49-351-2012 669 X-PGP-Fingerprint: DC 47 E6 E4 FF A6 E9 8F 93 21 E0 7D F9 12 D6 4E felawka@umelba.Triumf.CA (L. Felawka) wrote: > I had the same problem with FreeBSD 2.1.0-RELEASE. It was so severe > that I was unable to install from floppies (yeah, I know, pretty > low-tech) to a Pentium 133 machine. After installing from the network, > I found that the problem disappeared after I increased the loop count in > from 100000 to 500000 in the floppy driver polling loops. My guess is > that your machine is too fast. You've most likely only hidden another problem by this. I've just examined the assembler output for in_fdc(). It consists of 13 instructions. Assume one clock cycle per instruction (which is most likely a bold understatement since one of the instructions is an ``inb'' from the ISA bus which normally takes 1.25 µs itself) on a 200 MHz CPU, so the timeout will still be 6.5 ms. Now compare this to the required time to read one byte off a floppy at the lowest possible bit rate of 250 kHz: it is 32 µs. You see, the timeout is at least 200 times more than what would be needed. It's basically only a catcher for the ``floppy not ready'' condition that is needed since IBM dropped the READY signal from the floppy bus. -- cheers, J"org joerg_wunsch@uriah.heep.sax.de -- http://www.sax.de/~joerg/ -- NIC: JW11-RIPE Never trust an operating system you don't have sources for. ;-)