SCSI Termination in a 6100

Jorpho · Post by **Jorpho** » Sun Apr 17, 2005 10:28 pm

I have a Powermac 6100 into which I would like to install a 9.1 GB SCA hard drive that fell into my hands. There are SCA (that's 80-pin SCSI) adapters aplenty on eBay; I'm actually going to have to buy a second one since the first one I bought was too tall and the Powermac's cover wouldn't fit over it.

My other concern is that not all SCA adapters have terminators. Do internal Macintosh hard drives from that era have to be terminated? Can I put the internal CD-ROM on the end of the cable and terminate it that way? And if no one knows, can someone suggest a site where I could find out?

Post by **Cat_7** » Mon Apr 18, 2005 7:03 am

Hello,

Scsi termination can be achieved in at least four ways:
-A terminator at the last connector on the cable,
-Termination resistors on the drive itself (mostly three 8-pin red coloured resistors in a row)
-With a jumper in the jumper block on the electronics side of the disk, or on the connector side.
-With a terminated device at the end of the chain

And then there is the automatic termination of some devices...

You should google for the exact termination info of your particular disk, even if you are going to attach the cd-rom at the end of the cable.

this site is insightfull....:http://www.pcmech.com/show/harddrive/152/

Cat_7

Jorpho · Post by **Jorpho** » Mon Apr 18, 2005 1:24 pm

Yes, thank you, that was informative, particularly that bit about the drive requiring a proprietary adapter to terminate. I shall indeed investigate further. (My SCA drive is from IBM.)

The other drives in the 6100 are the stock Apple parts - an Apple 300i CD-ROM drive and an Apple 500 MB 50-pin drive. What puzzles me is that neither of them seem to have any jumpers or other visible means of termination. Is the CD-ROM drive supposed to be able to terminate the chain, or was it always only intended to be used as the middle device?