Some people may remember the 21Mb 'floptical' 3.5in disk drive sold by Iomega in the early 1990's. I have one on my desk right now, and it was a nice piece of kit. As well as using standard disks it can read and write to a special kind of floppy which has hundreds of concentric tracks etched into the surface. A laser on the R/W head reflects off of the etched track to be picked up by a sensor and by this mechanism the head can be positioned precisely.
Traditional floppy disks work by having an accurate stepper motor position the head without the aid of any feedback. This limits the number of tracks you can get on the disk to the accuracy of the stepper motor - and if you want floppies from one drive to read in another it had better have it's stepper motor in step (sorry!). In practice, this has meant keeping the inter-track gap on floppy disks to 135 per inch.
So, the 21Mb floppy disk achieved it's capacity by optical positioning of its head to achieve a far greater track density. Why didn't it take off? Because the drive cost £250 and the disks cost £25 each.
Now the technology has been made cheaper by 60%, and the capacity increased by 400% in the form of the ZIP. Multimedia files are now too big to fit onto a 1.44Mb floppy. The time is right.
But what about the competition? The Compaq drive just hasn't arrived, and looking at the size of the head they'll have problems miniaturising the unit sufficiently. The SyQuest 135 will always require expensive media. Sony's MD system hasn't yet appeared in quantities, though it has some advantages.
However, one of the main reasons for adopting the ZIP format is Iomega's willingness to license the production. See (See Computer Answers update 12-Jun-96)
There are currently four basic models of ZIP - internal and external SCSI units, a parallel port version and an internal IDE drive.
The IDE unit is small and neat, fitting into a 3.5in drive bay. However, I prefer my drive to be external which means either the parallel port or SCSI version. The parallel port is slower - though for many applications more convenient.
However, the external SCSI drive is readily connected to any Mac style SCSI connector (or a PC using a PC/Mac SCSI adapter cable) - a small price to pay for a big improvement in speed, not to mention getting your parallel port back!
Having the Mac SCSI connector gives to the added benefit of being able to transfer the drive and disks between PCs and Macintoshes.
For more information, contact Iomega - though some of their claims are a bit OTT!