----- Original Message -----
From: Pete Flugstad <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Sunday, February 28, 1999 10:02 PM
Subject: problems adding external JAZ (2GB) to Symbios 8751SP (53C825)
>Greetings all,
>
>This is technically not a Linux specific question, more along the
>lines of Ultra SCSI. But I'm hoping someone will have a quick
>answer for me anyway.
>
>I've got a Symbios 8751SP SCSI controller (53C825 based) - it's
>Ultra-Wide. I've got the following setup internally:
The chip on this card is a 53c875, not 53c825 ;)
>
> + Controller (ID 7)
> +--- unused connection
> +--- unused connection
> +--- HP 1.1 GB HD (Fast - Narrow - ID 1)
> +--- Sony CDU-76S 4x CD-ROM (Slow - Narrow - ID 6)
> +--- unused connection
> +--- Quantum Viking 4.5 GB HD (Ultra - Wide - ID 0)
> Termination Enabled - Term Power enabled
>
>For the Narrow devices, I have 68-50 pin adaptors.
>
>Now, this all boots and runs just fine. I have the Quantum running
>at 40 MB/s - the HP is at 10 MB/s and the Sony is at 5 MB/s - all as
>expected. The HP does NOT have Term Enabled, and I've removed the
>resistor blocks from the Sony (I assume that's correct, as I don't
>have and can't find online any docs for the Sony).
>
>Now, however, I'm trying to connect a Jaz 2GB drive (Ultra - Narrow -
>ID3) to the external connector, and it's giving me lots of grief.
>When I first tried this, I couldn't even get LILO to come up. Then
>I removed the narrow devices from the internal chain, and I could
>boot, but loading the kernel had a number of timeouts and other
>problems. Despite that I was able to boot fully - and shutdown
>right away again...
Hi Pete,
This is almost certainly to do with the way the auto-termination is done on
this card. Using both 68 way connectors disables all the terminators on the
controller. The cable sense circuitry only detects whether a cable is, or is
not, attached to a connector. It does not detect whether it is 50 or 68 way
unlike most other cards, at least on the revision of this card I have. If
one of the cables is only connecting narrow devices and only uses narrow
termination then there are likely to problems.
Using the internal 68 way connector and then connecting a 50 way device
using a 68-50 way adaptor or cable on the external connector will leave the
high byte of the bus unterminated at the controller.
To successfully use this card using both internal and external 68 way
connectors where one of the busses is 50 way requires a terminator to
terminate the high byte of the bus on the connector using the 50-68 way
adaptor/cable.
Otherwise you should connect narrow devices to the internal 50 way connector
and wide devices to the internal or external 68 way connector. In this mode
the card leaves the terminator for the high byte enable on the terminator.
This is the only problem I have found on what is otherwise an excellently
built card, but it is unfortunately a major failing.
Richard
...remainder cut
>
>Thanks,
>Pete
>
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