Multi Floppy PC
What is it?In short: a PC with a lot of floppies.
BackgroundI deal with a lot of different PCs. With "PC" I mean an IBM PC or compatible computer equiped with an 8086/8088 or better. In time these PCs had been equiped with several types of floppy drives:
- single side 5.25 inch 160 KB
- double sided 5.25 inch 360 KB
- 5.25 inch 1.2 MB
- 3.5 inch 720 KB
- 3.5 inch 1.44 MB
- 3.5 inch 2.88 MB
The above are not all type but they cover IMHO more than 98% of all used drives. The first one, the 160 KB drive, is rare and if needed, its floppies can be read by the 360 KB drive.
The 2.88 MB drive can only be found in some IBM PS/2 computers AFAIK. Are they rare? I don't know but having no PS/2 computer at all I never looked for one.
Exchanging data between the various machines could be a bit problematic so I took a Fujitsu ...., removed its CD player and installed an 1.2 MB drive instead. I would have loved to use a newer machine, like my IBM NetVista, but unfortunately I found out that all newer machines I had only supported but one drive. Bummer.
I installed Windows XP on this Fujitsu and used WinImage to create images from floppuies, when needed.
A better way?But things did not always go as smoothly as I liked: if I had troubles it was with reading 360 KB floppies by the 1.2 MB drive or reading 360 KB floppies With 360 KB drives that had been written by the 1.2 MB drives. So the idea rose to use more floppies.
This isn't a weird idea because the original IBM PC and PC/XT are able to handle four drives, if needed. But you needed a card that could handle four drives. And not only that, it would be able to handle 1.2 and 1.44 MB drives: other hardware and drivers were needed.
But why drivers, all 80286+ machines can handle 1.2 and 1.44 MB drives? Yes, they can, but they cannot handle four drives; just have a look at the setup.
I did find two cards in the end that were able to handle four drives and the idea rose to install both cards in one PC so I could handle eight drives: two of each type. There was software written by Sergey Malinov available but it was not tested yet and it needed changing some hardware of one of the cards. And then I ran into my Gotek floppy drive emulator: sorry, nine drives don't fit in this idea :(
The final idea!I had some troubles with using 720 KB floppies in a 1.44 MB drive in my XI-8088 so I installed a 720 KB drive as well and switched between them using a DPDT switch when needed. Due to a remark made on Vintage Computer Federation Forums , I began thinking about extending the above idea. And that resulted in two small PCBs that enabled a user to switch between six drives for each supported drive on the PC. Why "only" six? The reason is simple: there is a rotary switch available that has two inputs and six outputs for each input.
First: what has to be switched anyway? It is sufficient to switch between the "Motor enable" and "Drive select" signals of each drive. So for switching between two drives a DTDP switch is good enough.
The schematic and the boardThe schematic
I have to make a remark regarding the board. I found out that, -in my case-, it would have been better if I had rotated the floppy connectors 180 degrees.
The practiceThe very first problem I ran into was that I didn't have a PC case available that could contain up to nine drives. But I could lay my hands on two identical PC cases (thanks to Jaak Bartok from Belgium) that could contain up to four 5.25 inch drives and two 3.5 inch ones. I equped one case with a Pentium-III board, a 360 KB drive, an 1.2 MB drive and a 720 KB drive in a 5.25 inch holder in three 5.25 inch bays and a 1.44 MB drive and a Gotek in the two 3.5 inch bays. The fourth 5.25 inch bay was filled with a blindplate which on its turn held the two rotary switches.
The second PC case held a 360 KB drive, an 1.2 MB drive, a 720 KB drive in a 5.25 inch holder and a DVD drive in the four 5.25 inch bays and a 1.44 MB drive in one 3.5 inch bay.
Jaak also gave me a case that originally held eight SCSI CD-ROM drives. The idea was to put all floppy drives in one case. Unfortunately that didn't work out very well for several reasons so I stuck to the original idea, using the two PC cases.
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