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Re: ARGH, weird SCSI I/O errors on second/third drive on Debian/PPC

On Fri, Dec 27, 2002 at 06:49:50PM -0700, Jessica Blank wrote:
> I am having some weird, weird SCSI I/O errors. I'm running Debian/PowerPC 
> on an "Old World" (beige) Mac-- namely, a Power Mac 7300/180 (the 7300s 
> were sold overseas, and are uncommon in the USA; they are roughly on par 
> with the 7500s, I believe.. if not a bit higher-end) with a G3/220 CPU 
> upgrade.

The 7300 was available at least in the education channel in the USA. I
don't know about retail. It was basically a newer version of the 7500,
with only a handful of bug fixes on the motherboard, but a much better
processor installed by default. The 7500 shipped with a 601 chip, but
the 7300 shipped with a 604e. The 7600 was the same box with a 604.

> The system has worked fine for a long while. However, when I tried to 
> install some more SCSI drives into it (KNOWN WORKING drives), I get some 
> curious I/O errors which prevent me from using the system. The system only 
> seems to work properly when I use it with ONE hard drive. When I add more, 
> I get these problems.
> Please, could someone help me? Is this a termination issue? Is this a 
> known bug? What in heck is wrong with my Mac?

Well, the MESH chip that Apple used for SCSI in most of the PowerMacs
is a known piece of junk, and had a number of issues. The Linux driver
(unless someone fixed it while I wasn't looking) is pretty picky in
some cases about particular IDs and termination compared to the official
driver in the MacOS. You might try switching the drives over to the
other controller and see if they are more reliable. This board had
two SCSI chips, MESH and NCR53C94. The MESH is faster, but less reliable
in my experience. I haven't looked at a 7300, but on a 7600 there are
two SCSI sockets, one pointing up towards the top of the case, and one
pointing back towards the external ports (that doesn't have a plastic
frame around it, just pins). The one pointing towards the back is
wired up to the external port, which is controlled by the NCR chip.

	Brad Boyer

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