Subject: Re: aha0: DMA beyond end of ISA
To: Trevin Beattie <>
From: Michael L. VanLoon -- <>
List: current-users
Date: 11/09/1996 00:23:35
>I've also had another error come up a few times today; I have no idea
>whether or not it's related to the DMA problem:
>kernel: page fault trap, code=0
>Stopped at      _aha_collect_mb0+0x42:  andl    $-0x5,0xb8(%eax)

Quite likely it is.

The DMA "problem" is that you're trying to use an ISA SCSI controller
with more than 16MB of RAM.  You can't do that.

If you indeed have 16MB of RAM, your BIOS might be pushing some little
unusued block just over the 16MB limit.  You can either convince your
BIOS not to do this (depends on your BIOS), or hard-code the amount of

Or, you can find an unsupported patch that's been floating around,
that gives you a bounce-buffer band-aid, to make the thing work.

The best fix is to just get a better SCSI controller (and a better
motherboard if yours doesn't do PCI, EISA, or VLB).  This will not
only avoid the problem without resorting to hackish bounce-buffers,
but will also be _substantially_ faster.

Finally, you have the option of running FreeBSD or OpenBSD (or Linux)
-- systems which have native bounce-buffer support.

This is a well-documented problem.  Please see the appropriate FAQs,
and/or consult the mailing list archives on

  Michael L. VanLoon                 
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