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Date:      Wed, 4 Dec 1996 11:29:28 -0700 (MST)
From:      Softweyr LLC <softweyr@xmission.com>
To:        questions@freefall.freebsd.org
Cc:        mikebo@tellabs.com
Subject:   Re: 2.1.5R: aha0: DMA beyond end of ISA ?
Message-ID:  <199612041829.LAA27958@xmission.xmission.com>
In-Reply-To: <199612041658.IAA00184@freefall.freebsd.org> from "owner-questions-digest@freefall.freebsd.org" at Dec 4, 96 08:58:50 am

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mikebo@tellabs.com lamented:
> I have just put together a new Pentium PCI system with an Adaptec 2940U.
> I had the Adaptec 1542B ISA card left over, so I decided to use it to
> run my slow SCSI1 tape drives (an Archive Viper 150 and an Exabyte 8200).
> I jumpered the 1542B to Interrupt 14 so as not to conflict with the 2940.
> I don't know if this was necessary or not, but I did it anyway... I didn't
> change anything else on the 1542B, including the DMA jumpers, which I
> think are set to DMA 2 by default. (?)
> 
> Anyway, now every time I try to access the tape drives, I get:
> aha0: DMA beyond end of ISA: 0x19cc0a0
> st1: bad request, must be between 0 and 0
> tar: read error on /dev/rst1: Input/Output error
> 
> I think perhaps I need to jumper the DMA to a different number, so I'm
> going to try that now. But has anyone seen this before in a multi-SCSI
> controller system? Any suggestions would be welcome. Thanks!

Nope, read the message carefully.  Your 1542 is trying to honor a DMA
request at a memory address the ISA bus cannot reach:

	aha0: DMA beyond end of ISA: 0x19cc0a0

The ISA bus cannot address memory above 16M.  You need to configure a
new kernel with the BOUNCE_BUFFERS option, this will allow the 1542
driver to use a temporary buffer in ISA address space and then "bounce"
the requests to the user program.

--
          "Where am I, and what am I doing in this handbasket?"

Wes Peters                                                       Softweyr LLC
http://www.xmission.com/~softweyr                       softweyr@xmission.com



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