Kevin Diggs wrote:
> Paul,
> 
>     I have a Micropolis 3391 on the external bus that is running at 6.25 MHz (I
> believe this is the max it can run because of the clock input to the 53c94). So
> NetBSD is pushing the bus past its 5.0 MHz limit. This is clearly stated in the
> boot messages when the scan is done. If you are not seeing anything then your
> scanner is not running sync.

I don't think this is the problem: I do see the scanner and after 
a few patches could communicate with it.

>     I wonder if you could be seeing some kind of problem with that descriptor
> based DMA beastie (aka Grand Central) that sits in front of the external SCSI
> chip?
> 
>     Are there any macros you can set in the 53c94 driver to give more verbose
> details? What elese is on the external bus? BTW, I have an old Iomega bernoulli
> drive on the external bus on my 9600 that seems to work fine (it is async only).

we generated *lots* of output, the details of which I'll dig up.

>     Have you done any searches on the web to see if your scanner is a "bad scsi
> citizen"? Maybe this scanner is pulling some stuff that is giving the NetBSD
> driver for the external bus fits?

No, the scanner is fine, or at least it "works fine in linux[tm]" 
as my video card does.

>     How does it behave if you do a show-children from OF?

I haven't tried that. I'll see what I see there: may take me a day 
or so.

NB: I have copied Abel Deuring on this: he worked extensively on 
this, writing patches and interpreting the output.

> paul beard wrote:
> 
> 
>>Hey,
>>
>>I am trying to work out if I can use SANE on my old PPC 9500, and
>>seem to be running into some issues. If there is anyone who answer
>>  some questions about how the external SCSI bus works --
>>specifically if Apple engineered some idiot-proofing into it that
>>SANE may not be aware of -- please let me know.
>>
>>Here's what we're seeing: the external bus (this box has two built
>>in) sees the scanner and tries to use it, but gets reset during
>>the scan, and then it's lost until I restart it. There are some
>>miscommunications between the scanner library (SANE) and the
>>kernel: where the scanner says it's returning 161 bytes of data,
>>we only get 160.
>>
>>A related note from one of the developers who has been looking at
>>this:
>>
>>
>>>A more general SCSI question: (I assume that the folks who adapted
>>>NetBSD to the Apple hardware know this, but let us be sure ;) The reason
>>>that Apple installs two SCSI busses in many of their computers is to
>>>have a fast internal bus for the hard disks; this bus needs the usual
>>>careful setup: proper cabling and termination; for the external bus
>>>Apple managed to design the interface in an amazing "error-friendly"
>>>way. I have seen several absolutely wrong setups working flawlessly,
>>>like a 1.5 m cable at the end of the bus without a device and without a
>>>terminator. This can only work for slow transfer speeds, so I wonder if
>>>the NetBSD kernel really ensures that the speed of the external bus is
>>>really 5 MHz. Do you see anything related messages with dmesg or in some
>>>log files?
>>>
>>--
>>Paul Beard
>>8040 27th Ave NE
>>Seattle WA 98115
>>206 529 8400
>>
>>"Of ______course it's the murder weapon.  Who would frame someone with a
>>fake?"
>>
> 
>