Difference between revisions of "External floppy drives on the Spectrum +3"

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Revision as of 02:06, 27 November 2012

External Drive Connector

The "Disk B: connector on the +3 is slightly non standard and there is an error in the manual which adds to the confusion. The connector is rotated through 180 degrees so pin 1 is at the top right rather than the bottom left (looking in from the rear of the computer). The indexing slot is also at the opposite end to normal, instead between pins 31/32 and 33/34, this means that a keyed floppy cable will only fit in the wrong orientation unless the key is (re)moved.

External drive connector pinout (viewed from rear of computer)
33 31 29 27 25 23 21 19 17 15 13 11 9 7 5 3 1
GND GND GND GND GND GND GND GND GND GND GND GND GND GND GND GND GND
READY HD_SEL RD WR_PROT TRACK0 WR_GATE WR_DATA STEP DIR_IN MTR_ON NC DRIVE1 NC INDEX NC NC NC
34 32 30 28 26 24 22 20 18 16 14 12 10 8 6 4 2

Cable

An example of a suitable cable
Using a toggle switch to apply the Ready signal

To connect a normal PC floppy drive as "drive B:" to the +3 you need a ribbon cable with an edge connector at one end, and an IDC connector at the other.

Modern floppy drives don't provide the old "Ready" signal, so the ready line needs shorting to ground to signal to the spectrum that the drive is ready (adding a switch here is a good idea otherwise the spectrum won't start up unless there's a disk in the drive).

Drive

Any modern floppy drive will work as drive B: with the above proviso, you must create a ready signal for the spectrum otherwise it won't work. All modern drives are hard wired to appear as drive B: (hence the "twist" cable in a PC to make it appear as drive A:) so the cable is just a straight through wiring of all the signals.

Media

The +3 doesn't know about High Density (1.44MB) diskettes so you need to use Double Density (720K) ones, aka "blue floppies". These can be bought online, I don't know if they're still being manufactured anywhere or just new old stock. You can also cheat and tape over the hole on a HD diskette to make it appear as a DD one. This may or may not work, and the data may not stay forever (or it might be fine! but better safe than sorry if you save anything vaguely important on them). If you're just going to use a single diskette to "ferry" files from a PC to 3" disks then this is a perfectly adequate solution.

Disk Images

There are various software tools to write DSK images to physical diskettes, and individual files to +3 formatted diskettes. The other option (if you just want to "ferry" files from the PC to the +3 and save them on drive A:) is to format the disks to 720k DOS format and use a tool on the +3 to copy the files from the DOS floppy to the +3 format floppy in drive A: (or to the ram disk and then back onto a +3 formatted 3.5" disk in B:)

Writing Images

to access +3 formatted disks and format disks to this format on Windows NT you will need the FDrawcmd driver by simon owen. This will only work with real floppy drives, not USB floppy drives attached to laptops. A good utility for writing the images is John Elliot's dsktool.

Writing individual files

To write individual files to a +3 formatted diskette (or dsk file) you can use cpcxfs

DOS format disks

to access a DOS formatted 720k disk on the +3 you can use Garry Lancaster's MSDOS utility This will allow you to "log on" to a DOS format disk in drive B: and copy files from it to drive A: