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About SCSI and Adaptec AHA-2940UW

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First post, by Vendest

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Hi, looking for pointers regarding SCSI connectors and devices as I recently retrieved by chance an AHA-2940UW PCI controller card.
With no knowledge whatsoever about SCSI I needed to learn the very basics by simply reading the device manual and using some google power.
I installed and tested the card on a MSI KT3 Ultra with Win98, the card is detected during boot and I was able to update the bios from version 1.32 to 2.20.

My first question is regarding both the external and internal 68-pin connectors (16-bit wide) that seem slightly different from one another? I am not sure.
Do I need a cable with DB68 (HD68) connector?
https://www.cablestogo.com/learning/connector … odb68jumptocard

Secondly for internal drive such as Jaz or cd-rom, a 50-pin (8-bit narrow) seems to be the correct connector to use?

Lastly about the external connector, is it possible to use an adapter from 68-pin to DB50 (HD50)?

From my what I read, any devices connected to the board must be single-ended (SE). LVD is also an option considering backward compatibility to SE.

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Reply 1 of 3, by Disruptor

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Yes, such adapters exist.
You must not use all 3 connectors of this adapter.
You probably need to activate high-bytes termination when you use wide and narrow devices on different cable types (50 and 68 pin).

Basically termination takes place on both ends of the SCSI bus.
If your bus changes width from 16 to 8 bits or vice versa, you have to do a high-byte termination where it chances.

And, yes, the male wide connector from a cable fits on both female internal and extrernal wide connectors.

Reply 2 of 3, by Vendest

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Disruptor wrote on 2023-10-28, 15:49:
Yes, such adapters exist. You must not use all 3 connectors of this adapter. You probably need to activate high-bytes terminatio […]
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Yes, such adapters exist.
You must not use all 3 connectors of this adapter.
You probably need to activate high-bytes termination when you use wide and narrow devices on different cable types (50 and 68 pin).

Basically termination takes place on both ends of the SCSI bus.
If your bus changes width from 16 to 8 bits or vice versa, you have to do a high-byte termination where it chances.

And, yes, the male wide connector from a cable fits on both female internal and extrernal wide connectors.

Thanks for your help, it is clear now.
I do not seem to find many devices using the 68 pin connector.

Reply 3 of 3, by Disruptor

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Vendest wrote on 2023-10-29, 11:38:

Thanks for your help, it is clear now.
I do not seem to find many devices using the 68 pin connector.

No, because 80 pin SCA became more popular for server devices.
However, you may use SCA-to-68/50 adapters.

Cheap SCA adapters from China

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