Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!mnetor!uunet!seismo!mimsy!chris From: chris@mimsy.UUCP (Chris Torek) Newsgroups: comp.unix.questions Subject: Re: Problems with a tape-reader Message-ID: <7931@mimsy.UUCP> Date: Mon, 10-Aug-87 11:25:40 EDT Article-I.D.: mimsy.7931 Posted: Mon Aug 10 11:25:40 1987 Date-Received: Tue, 11-Aug-87 06:08:03 EDT References: <2642@lifia.UUCP> Organization: U of Maryland, Dept. of Computer Science, Coll. Pk., MD 20742 Lines: 39 Keywords: Tape-reader, BSD-4.3, BSD-4.2, UNIX, DLT In article <2642@lifia.UUCP> drabik@lifia.UUCP (Pascal Drabik) writes: > We encounter difficulties while we make use of our tape-reader >on a VAX-750 under UNIX BSD-4.3 operating system. >... When we are writing or reading files (which size is greater than >about 200 K bytes) on or from the tape, we get the error message : > ts0: hard error bn2020 xs0=350<6> > xs1=100000<6> xs2=100000<6> xs3=40<6> The important bit here is DLT, data late. > This error happens as well as in multi-user as in single-user mode. >It doesn't seem to be a problem of priority of the boards, nor a >hardware problem. Actually, it *is* a hardware problem, but one that is both caused and cured by software. >[hardware configuration] The configuration listed confirms the problem, which is that you have a 6250 bpi tape drive that cannot tolerate much Unibus access latency. The UDA50/RAxx driver in 4.3BSD was changed to set the DMA burst rate to 4; this is too high for some devices. 4.2BSD does not set the burst rate, which leaves it at 1. There are a number of solutions; the easiest is to lower the burst rate. The system may work with a burst rate of 3 or 2 words, or may require that it be set down to 1. This will slow all disk I/O through the UDA50 somewhat. Another solution is to install my driver (posted to some source group or another in April) and, if necessary, set the `bus hog' (ud_xclu) flag in the TS11 driver structure. Please do not now ask me for the driver; I will post changes or the updated version (whichever seems most appropriate) when I think it is ready---notably, *after* it has been tested on DW780s.... -- In-Real-Life: Chris Torek, Univ of MD Comp Sci Dept (+1 301 454 7690) Domain: chris@mimsy.umd.edu Path: seismo!mimsy!chris