90mm M.O. Adventures: Part 1 – Acquiring a Drive

In the mid-90s, there was a period when computer shops sold “optical drives”. That seemingly ambiguous name now referred to Magneto-Optical (M.O.) discs and Write-Once Read-Many (WORM) discs which were available in 130mm and 90mm cartridges at a range of capacities. While CD-ROM was already commonplace by then and CD-writers were just about to become affordable, the M.O. technology essentially competed with various super-floppy and floptical formats on the market as removable storage, often considered a “larger floppy disk” or a “removable hard drive”.

I wrote about these formats in an overview posting back in 2015 when I obtained a few samples of the media. But one thing I wasn’t able to do was to experience the technology first-hand. But this was soon to change.

A Breakthrough

By now, you probably know that I’ve been visiting Suruga-ya’s international online shop for a good few years, buying up a range of interesting technology including optical media and other equipment. While I have spent a small fortune there and I know the international site is a bit overpriced compared to other alternatives, it is a lot easier to navigate and I still feel I’m getting decent value for money.

Back at the tail end of 2024, I spotted that Suruga-ya had a good few listings for 90mm (3.5″) M.O. discs of various sizes, but they also had two drives listed too. There was an I-O Data drive of the GigaMO 1.3GB generation listed as not working and not able to recognise any discs and the price was a bit steep. The other was the Olympus TURBO MO miniEX III 640MO (MO643U6S). While there wasn’t much information available, it is a drive that is compatible with 640MB discs and earlier generations (so no 1.3GB/2.6GB GigaMO sadly). It has an onboard cache for faster response times and has a 3000rpm spin-speed according to specifications. Best of all, being a newer model, this one doesn’t require SCSI as it works off USB 2.0 (which should be faster than the disks themselves) and is nicely…