View Full Version : Wide Barracudas on Power Tower Pro internal fast SCSI

12-11-1999, 10:12 AM
I have purchased a used Power Tower Pro 225 used (on its way to me) and want to clear up a few things about installing two 9GB Seagate Barracudas (LW) on the fast internal SCSI.

I understand that the wide drives must go last in the SCSI chain, that I need a 68 pin to 50 pin adapter, and that they will (of course) be running in single ended mode.

I was looking at Granite Digitals site (scsipro.com). It appears that the adapter I need is their 5275 68 Pin Drive to 50 Pin IDC male-male adapter (correct me if I'm wrong). It states that this is to connect 68 pin wide drives to a standard 50 pin SCSI bus.

It also says this adapter has Active Termination. ('This adapter transfers all the proper signals and Actively Terminates those that are not being used').

First of all, does this mean I won't need to get a separate active terminator for the bus? I'm a little confused on the implications of this when using two adapters with two wide drives at the end of the bus (does the first connector terminate if the second isn't in use??). I'm sure I'm the first person here ever confused by SCSI http://www.digidesign.com/ubb/images/icons/smile.gif.

Also, will use of these two drives internally require adding a fan. I posted a similar question when I thought I was getting a Mac 9500, and was told I should, as the 9500 is plastic. Are the drive bays in the PTP metal, and if so does this mean an extra fan isn't needed??

Last of all (though I tried this one before with no responses http://www.digidesign.com/ubb/images/icons/smile.gif but here goes), is anyone using the 9BG Seagate ST39175LW (as apposed to the ST39153)? It appears that it is simply the next generation (18LP) barracuda. I'm tempted to just take my chances and try one ($254 at ecost.com!).

Thanks in advance!

Tom Dexter

12-11-1999, 01:11 PM
Thanks Steve.

Yes the fast bus inside the PTP is definately narrow. I was sure I saw a post of yours indicating the, when using wide devices on a narrow bus, the wide devices had to be placed last. From what your saying here, I take it that those adapters make the wide drives appear as narrow drives to the bus.

Also, am I understanding correctly that there is no need for any sort of active terminator, and that simply having that boot drive configured (with jumpers I assume??) to terminate the bus is all that is needed?

Thanks much for all the assistance.


Steve Rosenthal
12-11-1999, 07:42 PM
Right on both counts.

--Steve Rosenthal, Digidesign ETS

Steve Rosenthal
12-12-1999, 12:52 AM

That's the right part from Granite. The active term they're referring to only operates on the signal lines that are unused as the 16-bit (wide) signal path from the drives is stepped down to the 8-bit (narrow) signal path of the SCSI bus. Of course, I'm assuming the internal bus of the PTPro is narrow. If it's wide (because it might be a SCSI accelerator), you won't need to use any adapters.

Assuming the bus is narrow, and assuming the boot drive is already installed on the bus, you will use the boot drive to terminate the bus. (Most likely it's already configured to do so.) The boot drive will be connected to the last physical node on the SCSI bus, and your wide drives (which for all intents and purposes are now narrow drives) will be connected to any free nodes between the boot drive and the motherboard (or SCSI accelerator).

I'd jumper the drives for Force Single Ended, since they are LVD drives residing on a single-ended bus.

I don't know whether or not the PTP is plastic or metal inside, but I'd still condiser the fan kits.

--Steve Rosenthal, Digidesign ETS