Hacker's Corner - UniDisk 3.5 -> Apple 3.5 Conversion A Reversible UniDisk 3.5 to Apple 3.5 Disk Drive Labotomy Copyright © 1997 by Scott Gamon In response to the recent questions asking how to make a UniDisk 3.5 work like the Apple 3.5 drive...this also answers Randy Shackleford's comment of the Finder polling all drives - Apple 3.5 drives are polled SILENTLY while UniDisk 3.5 drives must have their drive motors intermittently activated. Upgrading your 3.5" drive: UniDisk 3.5 to Apple 3.5 modification You've upgraded from an Apple IIe with a UniDisk 3.5 controller to a GS and now you have a problem. When the UniDisk 3.5 is connected to a GS, it is dog slow. You have to set the interleave to 4:1 to make it run at a somewhat respectable pace when loading those large GS programs and data files, but this causes speed penalties when you take it to a friend's GS with an Apple 3.5 drive. Even worse, the drive is AUDIBLY AND VISIBLY POLLED by the Finder. It sounds terrible. Now the Finder polls every drive, true. But on the Apple 3.5 drive, this polling does NOT start and stop the drive motor. An Apple 3.5 drive is silent, but aware in a program such as the Finder. You wish you could magically transform your slowpoke, noisy UniDisk 3.5 into an Apple 3.5 (besides, this would make it usable as a convenient external drive on your Mac sometimes...). If your UniDisk 3.5 was manufactured in mid-1988 or later, you are in luck. The later UniDisk 3.5 models can be (fully reversible) modified to work like an Apple 3.5" drive. Make sure the power is off and the drive is disconnected from the computer. Get out your screwdriver set and get ready to roll! First, remove the screws from the UniDisk 3.5's case and remove the ABS plastic shell to expose the internal guts of the drive. Check the label on the mechanism: if it is a Sony model beginning with "#51W-" followed by two or three characters, your drive can be upgraded. If the mechanism is different, you are out of luck. :( Now that you have the UniDisk 3.5 opened and verified that the unit has the right model mechanism, take a look at how the internal components of the drive are put together. There are two circuit boards and the drive mechanism. The interface cable is connected to the lower circuit board and there is a ribbon cable that connects the top and bottom circuit boards together. First, unplug the interface cable from the lower circuit board. Next, unplug the ribbon cable (that connects the two circuit boards) from the top board. Finally, plug the interface cable into the top circuit board. When you are finished, the interface cable that was originally connected to the bottom circuit board should now be connected to the top one and there should be one cable dangling. Close the case by reassembling it with the screws and connect the drive to the computer. Now you can boot into the Finder and remove the UniDisk 3.5 driver from the *:System:Drivers folder and use the Apple 3.5 driver instead. Make sure to recopy all your 4:1 interleave disks to 2:1 interleave for fastest access. This modification is also useful for Macintosh, IIc Plus, and Apple IIe with SuperDrive controller users. If you are still suffering the rattling noise and slow access of a UniDisk 3.5, why not give this modification a try? It is completely reversible should you ever need to use the drive on a IIc or a IIe with a UniDisk 3.5 controller again. -Scott G.