SCSI confusion - connect a 68-pin external device to my SE/30? What software is required for CD-ROM?

[aeberbach]

I have a big old external SCSI enclosure with 16-bit 68-pin connectors on it. From what I read the SCSI standard is supposed to interoperate and if the physical connection can be made that should operate as an 8-bit SCSI peripheral also. So if I was to find a Mac 25-pin M to 68-pin SCSI M cable I should be able to connect it? Another possibility might be a regular Apple SCSI cable with an adapter converting Centronics 50 F to 68-pin M?

Then once the physical connection made what does a System 7.5 Mac need to see device connected in this way - I expect hard drives just show up with Lido or similar. How about a CD-ROM drive, they should show up as read-only once a readable CD is inserted? How were other devices such as scanners managed?

(I would buy an external SCSI housing with Mac-style Centronics 50F connectors but they are not common)

 

[MrFahrenheit]

As I have found out, and been further educated on here with, SCSI termination is an issue with using different SCSI versions together. The drives drop down to the lowest common SCSI version but termination needs to be dealt with. 
 

The 16 bit wide bus needs to have the high lines terminated as well as the low lines with a regular SCSI 1 terminator. If you’re connecting it to a Mac SE/30 you’ll have to terminate more than just a standard 50 pin centrics type terminator can do. I don’t know the solution I just know the problem. 

 

[NJRoadfan]

I think a DB-25 to HD-68 cable should work. High byte termination should be a non-issue, just make sure the drive is the last device on the chain and properly terminated. Also the drive must be set to "single ended mode" and/or "narrow mode". and must only use a device ID from 0-7 (0 is typically assigned to the internal HD and 7 to the controller). ID 8-15 is only available for wide controllers.

Centronics 50F enclosures should be VERY common. They are standard SCSI and were made for many years. The easiest way to get one is a "broken" external drive of some sort, just swap in whatever drive you want.