When this tutorial was written, I had no new drives to add so I'm going to connect the existing PowerTower Pro drive to the 2940UW card, disconnecting it from the stock motherboard SCSI controller.

Although I don't like putting slow devices like CDROMS, ZIP drives or Scanners on a fast PCI Card (they are not taxing the stock SCSI interface), some readers may want to connect all stock SCSI devices to the PCI card. The easiest way to do that on the PowerTower Pro would be to remove the existing SCSI connector from the motherboard and connect it to the PCI SCSI card. As shown at the right, it's in the upper center of the motherboard - to the right of the CPU card and Power Supply.

For the older Apple Towers (8500/9500) it's far easier to just use a new SCSI cable. The 8500/9500's have the cable routed such that you cannot easily remove it. To free the existing SCSI cable in the 8500 for instance, you have to release the top mounted speaker assy (a tab holds it down), and then remove the cable from under it. If fact, you may have to remove the motherboard (instructions are in my 8500 cache upgrade tutorial).

If you disconnect drives from an existing cable, make sure you take note which drive was the last device attached to the cable - you'll need to connect it as the last device on the cable from the 2940UW as well to ensure proper termination. This way you don't need to mess with drive termination jumpers. SCSI rules require that the last device attached to the cable be terminated - so it's important to connect the devices to the 2940UW cable in the same order as before. If you leave any devices on the stock SCSI cable, remember that the last drive on that cable also must be terminated (have its termination jumper enabled).

Do not force the card, but apply firm pressure after the card has entered the PCI slot to ensure it is fully seated. If the card binds, remove it and try again, watching for alignment of the connectors carefully.

(Note: Most Apple Macs do not use screws to retain PCI cards to the case, only the prev. mentioned spring tabs retain the card).

During testing I discovered that performance varied significantly depending on which PCI slot was used. Best performance was found when the card was installed in the lowest PCI slot of of the PowerTower Pro. Peak performance was almost double and sustained speeds were 5MB/sec faster in this slot than in a slot two connectors up (top of 2nd PCI bus in the PTP).

Apparently the lower slot supported busmastering, where the other did not. That's the only reason I know of for the performance difference. Only an Imagine 128 Series 2 Video card was installed - in the upper PCI slot (the first PCI bus of the PTP). All other slots were free . Duplicate tests with the ATTO PCI SCSI card showed identical behavior (proving it was not a specific card issue).

Now that the 2940UW is installed, Attach the ribbon cable to the 2940UW connector (for Narrow scsi used in this example, the raised Keying notch on the connector mates with a slot on the card connector). If possible, orient the cable as shown for reduced cable bends - one end of the cable will allow this better than the other.

Note how the cable attaches with a straight exit from the card in this photo. Some bends can't be avoided, but try to minimize them and avoid folds or creases (although PowerCC seemed to love to fold the cable). In most cases proper routing through the chassis can minimize the number of bends, and take care in metal chassis such as the PowerTower Pro to not nick the cable on any sharp metal edges. If you do - replace the cable, do not use SCSI cables that are cut or damaged.

Make sure that the last drive on the 2940's cable is terminated.

Make a final visual check of all SCSI connectors to ensure they are fully seated squarely in the mating connectors of the card and drives. I run my finger across each ribbon cable connector, pressing down firmly to ensure they are bottomed in the mating connectors. If the connectors are not fully seated the system will not boot - and it's the first thing to check should the Mac fail to boot on initial power-up.

Now that all the hardware is installed and connected, we can proceed to the next page of the tutorial where we power up the Mac and install the Adaptec Power Domain control software.