Rusty on my SCSI Etiquette.

[l008com]

It's been a while since I've worked much with SCSI. I've got an external hard drive here with a bunch of files I need to copy off of it. 

I'm trying the easiest way first, using my old SCSI USB adapter and trying to copy them right off, to a modern Mac. But alas, no joy. This is how this USB SCSI adapter always is. Sometimes it works. Sometimes it doesn't work. Sometimes it works but you have to let it sit plugged in for 15 minutes, until suddenly the SCSI drive will show up. 

First some basics. I know the top and bottom ports are for chaining, but does it matter which is which? Does one have to be "towards" the host, and not the other?

Second, with a setup like this, is an external SCSI terminator needed? I would assume yes, but the customer told me he recently attached this thing to his old PowerBook with just one cable, and no terminator, and it worked great. 

As you can see, I do have an old PowerMac nearby, and I do have cables to connect to IT instead of my USB adapter. That will be what I try next....

 

[uyjulian]

The port doesn't really matter, but you need a terminator on the bus. Some devices have a built-in terminator, while others will require an external one.

 

[l008com]

I figured I needed one. But that begs the question, how did it work for the customer without one? 

There are no termination "switches" on the back of this drive, but there is an ID switch that lets me pick from 1 to 6. 

 

[sstaylor]

Yeah, there's this whole thing with SCSI that you might be able (probably able) to get away with no termination and stuff like that; but it's probably going to be iffy. Some devices like to be at the front of the chain, others at the end.  All kinds of weirdness. Hence the term "SCSI voodoo".  But you'll have best performance and fewest problems doing stuff by the book, and that means termination at the end of the chain.

 

[l008com]

Ok so first I tried connecting the external drive to my USB adapter. Played around with that, got nowhere.

Then I tried connecting the external SCSI drive, via SCSI, to my old powermac. Played with that for a while, got nowhere. 

Then I gutted the external drive, took the drive out, and hooked it up to my powermac's internal SCSI bus, putting an OEM apple drive after it on the chain. All OEM apple SCSI drives terminate (as far as I know). Then I started thinking, this probably won't work because they're both going to try to be ID 0. But before I could think about my solutions to that, it worked! It booted up, and the drive I wanted to use showed up, the other drive that I was only using to terminate, did not. So I copied the whole contents of the drive (A whopping 150 MB) and everything seems good. I should probably buy a pair of terminators so this will go smoother in the future. But there probably will not be a future, this is probably the last one ever. So.... *shrug*

 

[l008com]

How rude of me, to not include a photo in my last post!!