[6006] in linux-scsi channel archive
Re: problems adding external JAZ (2GB) to Symbios 8751SP (53C825)
daemon@ATHENA.MIT.EDU (lma@varesearch.com)
Mon Mar 1 17:43:32 1999
From: <lma@varesearch.com>
Date: Sun, 28 Feb 1999 20:15:34 -0800 (PST)
To: Pete Flugstad <pete_flugstad@icon-labs.com>
Cc: linux-scsi@vger.rutgers.edu
In-Reply-To: <36D9BCF8.FFC3133E@icon-labs.com>
There are multiple kinds of 68-50 pin adapters. The external 68-50
pin adapter you need must terminate the upper bits on the SCSI bus.
Most 68 to 50 adapter cables simply leave the unused wires unconnected.
(Your internal 68-50 pin adapters probably do this.)
Larry
Pete Flugstad writes:
> 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:
>
> + 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...
>
> Finally, I jacked the Quantum down to 20 MB/s, (using the Symbios
> BIOS setup), things got better, and I could connect the other internal
> devices. But it's still having occasional timeout problems - say
> one ever 5 to 10 minutes, depending on how heavily I use thing.
> And they are all still on ID 0 (the end of the chain). This causes
> the controller to reset the bus, which basically lock severything
> up for 5-10 seconds. Needless to say, I'm not very comfortable with
> this.
>
> Now, the external cable is fairly high quality - cablestogo.com,
> part # 08252 - SCSI MD68M - MD50M. It fits nice and tight. The
> internal cable also seems of reasonable quality; it's a 7 device
> cable I got from oscarno1.com. The 68-50 pin adaptors also seem
> reasonable quality - oscarno1.com again. I have the Jaz setup
> with Term enabled (rather than their Auto setting).
>
> The internal cable is probably about 1 meter. The external cable
> is about 3 feet. Could the length of the chain be causing me
> problems? I've seen references that indicate that the total SCSI
> length should be less than 1.5M for Ultra - I guess I'm exceeding
> that slightly. Would moving all the internal devices closer to
> the controller work. Are there any issues with the dangling cable
> out there? Should I get a smaller (4-device) cable?
>
> I've tried all kinds of things to try and get this to work,
> but I haven't had any luck. I really want to get things working
> reliably at their correct speeds. Any suggestions would be
> greatly appreciated. I'm already toying with replacing the
> CD-ROM, since it's the only slow device, but I don't think that
> will help much.
>
> Thanks,
> Pete
>
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