Text File

Acincy.146 fa.unix-wizards utzoo!duke!cincy!chris Thu Jun 25 21:13:08 1981 An intriguing problem

I have been tinkering with some drivers on our (V6) system and have unearthed an interesting phenomenon. Perhaps one of you can explain it to me. We have a Ramtek RM9200 Display Processor hooked up to our UNIBUS through an interface that looks almost like a DR11B. Until recently, the driver stole a system buffer and copied the user's data into it, and then did DMA from the system buffer. It worked fine -- except that it seemed slow. I thought it would be better to use physio to do DMA direct from the user's buffer. So I rewrote the driver and installed it. It seemed to work fine. Then the system got busy, and I started getting data late errors from our RK drive. We swap there, and the system has since crashed numerous times from I/O error in swap. I don't understand why this has cropped up all of a sudden. The UNIBUS is laid out as follows:

11/60 KL-11W (console) RK11 spl5 RP11 spl5 Ramtek spl5 DZ spl4 DZ spl4 DR11K spl4 TM11 spl5

I get no complaints from the RP11 (it's really a Plessey controller --by the way, don't ever buy one-- hooked to a 300 MB CDC drive that emulates 6 rp03s), but the RK goes nuts. Any suggestions? I would like to leave the Ramtek at spl5, because we do highly interactive work with it, and the general feeling is that it is as important if not more important than the disks.

----------------------------------------------------------------- gopher://quux.org/ conversion by John Goerzen <jgoerzen@complete.org> of http://communication.ucsd.edu/A-News/

This Usenet Oldnews Archive article may be copied and distributed freely, provided:

1. There is no money collected for the text(s) of the articles.

2. The following notice remains appended to each copy:

The Usenet Oldnews Archive: Compilation Copyright (C) 1981, 1996 Bruce Jones, Henry Spencer, David Wiseman.