Date: 4 Jul 1997 19:24:40 -0000 From: mark thompson <thompson@squirrel.tgsoft.com> To: freebsd-hackers@freebsd.com Subject: more corruption Message-ID: <19970704192440.4695.qmail@squirrel.tgsoft.com>
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I have written a couple of times about data corruption problems on my
floppy drive, which turn out to only happen when the IDE drive is also
in use. The symptoms include data being moved from their proper position
by a few bytes. I found this really fascinating note on the partition
magic install disk, which i quote here without permission of any kind -
because i think this may be a concern to users of FreeBSD on PCI
computers (like mine). Personally, i have decided to junk my IDE drive.
-mark
DMATEST 1.01 - Dual-DMA Data-Transfer Reliability Test
Copyright 1995 PowerQuest Corporation
All Rights Reserved
PowerQuest Corporation
1083 N State
Orem, UT 84057
voice: 801-226-8977
fax: 801-226-8941
email: scotl@powerquest.com
***** PLEASE READ THIS VERY CAREFULLY!! *****
IF YOU DO NOT, IT COULD COST YOU YOUR DATA! ALL OF YOUR FILES
ON ALL OF YOUR DRIVES COULD BE DESTROYED BY A DMA-TRANSFER BUG!!
We have found a serious data-corruption bug when using dual-DMA transfer on
some computers. It shows up when multitasking between the hard drive and
another device such as a floppy drive or a network. When this happens, the
data can get shifted by 2 or more bytes.
This has serious implications, and has already destroyed many partitions. If
the operating system happens to write to the hard drive at the same time that
you access a another peripheral device (floppy, network, CD_ROM, etc.), the
drive can become corrupted, and the entire partition destroyed. Every
PCI EIDE system we have in house has this problem.
We have found a work-around for some BIOSes: Changing the "PCI IDE prefetch
buffers" BIOS setting to DISABLED prevents the error. Unfortunately, not
all machines with the problem allow this setting to be changed by the user.
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