Suggestions, questions, acclamation, or simply curiosity about who that guy is you might want to place here:

To fight spam, I'm running RBL-based filtering and Greylisting, so if your ISP's mail server is blacklisted or doesn't play according to the SMTP RFC, you might encounter bounces.

For some kind of reason (there must be one...) the so-called Japanese 3.5" floppies spin with 360rpm like the old 5.25" drives instead of 300rpm as the rest of the world does. Casio, in their eternal wisdom, decided to use such a non-standard configuration.

If you have a working JU-386 and you want to make it PC-compatible in terms of rotation speed, you need to change the settings at JP1 on the motor PCB (not controller PCB!) as shown in the below table. Installing a switch at pins 1/2 therefore allows you to switch between conventional 300rpm (and therefore allow disks being read/written with your PC) and Casio's own 360rpm for legacy disks.

Unfortunately, almost no floppy I've seen so far—apart from the aforementioned Panasonic JU-386 used in the FZ-1—has a "speed select" switch although the commonly used motor controllers have such an input which put me instantly in hunting mode when opening a TEAC FD-235 (of which I got a few so an eventually killed drive wouldn't be that big issue here). Having done so, I played around with a Mitsumi/Newtronics D359.

In case you did the same with other drives, just let me know and I'll include it in the below table.

Looking at the datasheets of various Rohm and Sanyo FDD spindle drivers, the following applies:

The LB1817M gives even more flexibility and provides a total of 3 divider inputs (MS1 to MS3), resulting in the following speed table:

In case you want to upgrade machines to supporting HD disks even though their controller only copes with DD speeds (like the WD177x line of FDCs or PAULA on the Commodore Amiga), you have two essential options:

• Use switchable input clocks (might eventually require switchable PLL components, too) and go for uniform 300rpm setting, this is what e.g. this approach describes.
• Tweak the Rohm BA6492 or Sanyo LB1817 to half the clock rate and then switch between 300 and 600rpm mode, resulting in 150 and 300 rpm operation.

Back in the days, a number of standards coexisted. Hence, the disk-drive vendors put more or less effort in making a drive configurable for either Shugart or PC use. If you have the choice, go for these drives:

• Panasonic JU257 Rev. (I'll look it up next time I open my DSS-1, promised): this wonderful drive is fully jumperable
• TEAC FD235HD Rev. 3xxx: also this drive is fully jumperable, but makes an adventure game of it.
• TEAC FD235HD Rev. A529: this drive is also fully jumperable, but makes even more an adventure game of it. Close D2/E2 (RDY# to Pin 34) and remove E1/E2 (DC# to Pin 34). Also close A1/B1 (Pin 10 to DS0).
• Mitsumi/Newtronics D359Tx: once you remove the bottom cover, you'll find solder-in jumpers for configuration. Not as comfortable as the JU257, but never the less flexible.

• Rev. 218-U (IR4N09A): Select Drive 0 via jumper; remove all other jumpers. Remove solder-jumper at S27 (DC#) and close the solder-jumper ad S29 (RDY#).
• Rev. 4291 and 4430 (T4A34F): Select Drive 0 via jumper; remove solder-jumper S18 (DC#), close solder-jumper S19 (RDY#).
• Rev. 5291-U (T4A34F): Select Drive 0 via jumper; cut trace at pin 69 (DC#), wire pin 68 (RDY#) to the floppy connector, pin 34.
• Rev. 6291 (BH95060GKS2): Select Drive 0 via jumper; cut trace from floppy connector pin 34 to floppy controller and rewire pin 34 to the controller pin 10 (RDY#).
• Rev. 7291-U5 (BH95060GKS2): There's two solder-jumpers for selecting the drive ID, solder it to DS0, rest see 6291.
• Rev. 8291-U5 (TRN9510A): Unknown (yet) for lack of controller datasheet. Judging from a published NEC FD1231H hack, RDY# is on pin 32, DC# on pin 55.
• Rev. A291-U5 (TB604HF): Unknown (yet) for lack of controller datasheet.

Likewise, a number of revisions of the Panasonic JU257 and the Mitsumi/Newtronics D359 exist that are more or less easy adjustable.

(In case you're an Amiga user who came here by Google, the above procedures apply to you, too, but don't forget to wire DC# to floppy connector pin 2. The Amiga needs both!)

Here you'll find a plethora of information and further links -- most of it in German, but your favorite online translator should do a half-way sensible job here.

/READY is something unsual to the PC world -- according to the service manual, the FDD grounds this signal when all of the following conditions are satisfied:

• all the voltages are supplied
• the floppy disk's rotation is over 84% of the normal rotation speed
• a floppy disk is loaded
• /DIR is set to 0
• head is on track 0 at power on