troubleshooting Question

IBM SCSI W drive in External enclosure not recognized

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lmbrtnsh asked on
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I am putting together an external enclosure to contain two 4.5GB dirves. The first drive (which is working fine) is a Seagate Cheetah ST34501W. The second drive (with which I am having difficulty) is an IBM DDRS-34560 also a Wide drive.

The external box has Centronics 50 pin connectors (the big printer type); I am exiting the computer via a 50 pin to 68-pin adapter port attached to the Narrow bus on an Adaptec 2940UW (Onboard using the 7880 chipset).

The external interface cable is an HD68 to Centronics 50 entering the external box. Internally, ribbon cable and 50-pin connectors (using 50-pin to 68-pin adapters for the two hard-drives) loops back out to an externally supplied end of chain terminator.

The following ID's are set via jumper:

IBM DDRS-34560 -          ID = 1
Seagate ST34501W -        ID = 2
Plextor 12/20X CD-ROM -   ID = 4
Yamaha 4260 CD-RW       - ID = 5

Note: Termination is not set on any of the drives or CD units; only externally.

Set in Adaptec SCSI BIOS:

Wide negotiation is set to No for ID's 1 - 5
Start Unit Send is Yes for IDs 1 - 5 *

*(Note:the Seagate didn't care about this, but the IBM did, even when it was originally inside the computer.)

The DDRS additionally has engaged jumper settings for Autospin enable, and SE mode enable, i.e., both settings are enabled. I have tried the drive without these enabled, as well.

Symptom: After POST, the Adaptec startup recognizes all devices except the IBM. If the drive is placed inside the computer (not externally, but as the boot drive) it is recognized. It has been both low-level formatted and fdisked with two 2+GB partitions (FAT16).

Another friend has noted recognision failure with a similar IBM drive.

Does anyone have any experience with these drives where all the bases seem to be covered, but the drive still doesn't show up?

I'm pretty certain the external box is terminated correctly, otherwise the Seagate drive would fail recognision as well, correct?

I don't believe active, high-side termination is required for the IBM and not for the Seagate - anyway setting the SCSI BIOS to narrow should take care of internal to external negociation over the 50-pin narrow bus (or why would the Seagate work?).

If further information or setup details are required, please let me know and I will forward them in another posting.

If anyone has had a successful outcome with this type of situation, I'd appreciate some guidance as I'm pretty close to packing it in with the IBM drive.


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