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From: evans@syd.dit.CSIRO.AU (Bruce.Evans)
Newsgroups: comp.os.minix
Subject: Re: fix to diskcheck(1)
Message-ID: <1990Sep25.115315.1466@syd.dit.CSIRO.AU>
Date: 25 Sep 90 11:53:15 GMT
References: <31035@nigel.ee.udel.edu>
Organization: CSIRO Division of Info Tech, Sydney, Australia
Lines: 14

In article <31035@nigel.ee.udel.edu> archer%segin4.segin.fr@relay.prime.com (Vincent Archer) writes:
>While I was fixing the cache code, I improved the cache use: If you use a
>raw device (like /dev/rh1b - rhd1 for PCs), no cache purging is necessary

Raw disk devices are not implemented on PCs. They almost work anyway. You can
try mknod'ing the disk devices as character devices as well as block devices.
Various things go wrong. The drivers that use DMA (floppy, xt_wini, bios_wini
for XT controllers) will fail when the user buffer crosses a 64K DMA boundary.
The floppy and xt_wini drivers will panic from this; bios_wini will return an
error. The at_wini driver works. All the drivers require a too-small i/o size
of 1K. This results in the raw at_wini driver being about 25% of the speed as
the block at_wini driver on my system.
-- 
Bruce Evans		evans@syd.dit.csiro.au