6 Mar 2010

NeXT Optical Discs

NeXT Software Release 1.0a

When I was in middle school, around 1987-88, a kid brought in a strange plastic box that contained a shiny round disc, rattling around within it. His father worked at NeXT, down in Silicon Valley, and he had given his son a (very) early example of the infamous Canon optical disc that would define the first NeXT computer.

Steve Jobs’ vision for the future was simple: without any other kind of permanent storage, users would keep their entire universe of files and operating system on a disk like the one seen above. They could move from machine to machine, taking with them hundreds of megabytes of digital files. This was a very neat concept in the late 80s, when hard disks were expensive and small. Manufactured by Canon, the magneto-optical drive would be one of the Cube’s defining aspects. A perusal of the underlying technology is rewarding — as the name implies, the discs combined magnetism and the optical spectrum in a unique way: a laser heated part of the disc to the curie point, a temperature where the polarity can be flipped by electromagnets. That same bit can then be read by the laser (at much lower intensities) and its value determined by the varying properties of how light reflects from magnetized materials. Unlike traditional Winchester drives, they were as immune to dust as an audio CD, which made them perfect for transportation.

The reality didn’t quite live up to the promise — the optical system was four times as slow writing to the drive as it was reading from it, which mean that when virtual memory (always on in the Mach system) paged out to disk it brought the machine’s performance to a halt. NeXT eventually included small, inexpensive 40megabyte hard drives in the cubes, preconfigured as swap space (and indeed too small to hold the operating system by itself.) I suspect the most useful cubes had the optional 330 or 660mb internal SCSI drives installed. Certainly by the time the Motorola 68040 had replaced the ‘030, the optical disc system had become more of a curiosity than a feature, and the last variant of the cube (NeXTDimension Turbo) actually removed support for the oddball device.

NeXT Software Release 1.0a

The ‘040 cube I had in Chicago in the mid-1990s still had an optical drive in it, but like most other examples, it had long since stopped functioning. There were a plethora of problems with the device, including an unfortunate cooling design of the cube itself which led to sensitive lenses and other components being coated by dust rushing into the unguarded disc slot. (NeXT eventually recommended reversing the flow of the fan at the back of the cube, so that air was pushed out of the slot, not in.) But even ‘new old stock’ optical drives have been known to be defective, possibly due to off-gassing of plastic components dulling actuator positioning templates.

It’s anyone’s guess how many functioning Canon optical drives exist at this point. Though the Cube used the standard SCSI connection for drives both internally and externally, the connection between the optical drive and the motherboard was proprietary, and declaimed as such in the the technical information NeXT published about its own hardware.


Interoperability standards for magneto-optical drives never really existed during the timeframe that the Cube was sold — even Mac users had to stick to one vendor for both disc and drive — and so it’s doubtful that any other kind of drive could read these orphaned discs. Were such a drive to be discovered, recent progress in emulating NeXT’s UFS file system under Mac OS X (its distant descendent) have at least made the files themselves theoretically recoverable.