VOGONS

Zip Drive on a SCSI Chain

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First post, by BooseF16

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I am building a retro computer and trying to have an external SCSI Chain on it and I am running into a problem when I add a SCSI Zip drive to the end of the chain.

The Adapter is AHA-2940U2W and it detects all devices when the SCSI BIOS loads successfully.

The External Chain is a Jaz Drive at ID 4 and a Zip Drive at ID 5 with Termination On.

When I boot in this configuration the boot hangs at after the SCSI BIOS loads successfully. If I remove the Zip Drive and keep just the Jaz drive it boots fine into Windows 98 SE.

My initial thought is the Zip drive runs SCSI-1 and it connected to a WIDE external port on the Adaptec Card. I turned off Wide negotiation for the Zip ID and got the same results. I tried it with Wide negotiation off for the Jaz and Zip since they are on the same chain and got the same results.

Right now my though is to buy a 50 pin internal to external adapter and plug those devices into the 50 pin SCSI-2 chain inside the computer.

Any thoughts?

Reply 1 of 4, by ElectroSoldier

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Even though the Zip drive has its terminaton turned on it can only terminate the narrow side of the bux it cant provide the proper high byte termination the bus requires.
The Jaz drive is SCSI Ultra so provides this termination while the Zip drive is SCSI-1/SCSI-2 so provides only Narrow termination.

There are a few options.

Put the Jaz drive at the end of the cable and see if it terminates the cable
Put an active terminator on the end of the cable
Put the 50 pin connector on the 2940U2W on the outside of the case and use that to connect the devices as the 68 pin external connector is the U2W channel and so its isolated from the narrow side.

personally I would route the internal 50 pin cable outside and use that via an adapter but thats because I would be using the U2W for a local fixed disk.

Reply 2 of 4, by BooseF16

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Hi ElectroSoldier,

I tried what you recommended and moved the Zip mid chain before the Jaz and moved the Zip Termination off and terminated at the Jaz. I can get it to recognize all the devices on the chain now, but then it can't find the boot drive at ID 1. I've heard the Zip can be finicky when connected to a wide bus; even with Wide negotiation set to off for that ID. I'll try connecting the Zip to the 50 pin once the adapter gets here. Worst case I can connect the Zip to a Zip Zoom that I have as well, I'm just trying to put all the devices on a single chain.

Thanks for your help!

Reply 3 of 4, by ElectroSoldier

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This is exactly what I would expect given the setup you have and is why I concluded my last post with the line that I did.

Where is ID1 plugged into?
If internal connector is that cable terminated correctly?
Is ID1 disk wide or narrow (68pin or 50pin on the device)?
What is the exact chain order? (Card external connector? - Card internal connector?)
Does ID1 show up in the list of devices on card BIOS post screen? are there any problems at this point?
Does ID1 drop when Windows tries to load?

Reply 4 of 4, by BooseF16

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I tried changing the chain order, wide/narrow, as suggested and no avail. I got an external adapter and connected the Zip to the narrow port and it worked. I read some other stuff about the zip not liking to terminate an Ultra2 or wide chain.
Thanks for the input!

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