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The MGT +D interface was one of a few disk interface solutions that appeared for the Spectrum in the mid-to-late eighties. Given the failure of Microdrives, and the lack of an official disk interface (the +3 appeared in 1987 but it’s use of the quirky 3″ disks was not favourably looked upon), several manufacturers decided to take up the mantel themselves.
The +D was a successor to Miles Gordon Technology’s DISCiPLE interface, itself a reaction to the lack of disk tech for the Speccy. However, that device was overly complicated making it pricey and unreliable.
The newer system was to prove much more popular and established a good following in the market, not least because it made use of the far more popular 3.5″ floppy disk. It also had a Centronics printer port, which its predecessor also had. It also offered a straightforward install solution using a MGT +D on Spectrum Computing.
When MGT ran into financial problems, Datel licensed the design and carried on producing the equipment, but unfortunately the system was never embraced by commercial manufacturers and therefore remained mostly in use as a means for ‘backing-up’ and distributing software. This backing up process was initiated by using the magic button on top, which allowed the exact state of the Spectrum to be dumped to disk, for reloading later (much like the Multiface). This could then be duplicated and distributed and all the recipient would need is another +D interface.
The high capacity of the disks made the system popular in the homebrew scene and in territories outside of the UK where clones popped up and fed the demo scene, where it competed with the Beta disk interface.
Datel released the designs into the public domain and nowadays clones are still available on sites such as RWAP Software and Byte Delight PlusDlite.
Real hardware with Gotek
The quickest way to start is to copy across all the DSK files to your Gotek, and connect it up to the interface. When you have powered on select either the plusd_system_1_drive.dsk (one drive, no printer) or plusd_system_full.dsk (two drives, with printer). If you have a different combination, or you would prefer to use a different disk geometry to 80 track, double sided then you will need to run the system config program.
Pressing the top bottom will take a snapshot
If you wish to use Plus D v2 on Fuse (or any other compatible emulator), place the plusd.rom in your roms folder (see the emulator documentation on the location). It isn’t normally included in the install, so this step is required.
Select either the 16k, 48k, 128 or +2 model and under disk options add the +D interface. After reset, insert the plusd_system_full.dsk in drive 1.
To take a snapshot, trigger an NMI.
When you are ready to boot, enter BASIC and type RUN. After a few seconds of loading you will see the OK message and you are ready to go. Refer to the manual for full instructions, but for a quick test type CAT 1 to see a directory listing.
Try to avoid writing to the boot / system disk; it is advisable to switch to one of your other disk images (feel free to copy blank.dsk liberally) immediately after booting. It is also a good idea to copy the bootstrap code to a blank disk (if you have two drives) with the command SAVE D1 “+SYS 2a” TO D2. This has already been done on blank.dsk.
Trigger the snapshot, and the border will change colour for a few seconds. Then press 1-5 according to your preference. Wait until the border stops moving and press Y to save to disk or print a copy. Snapshots will be saved directly to the disk, and you may wish to rename them later to something more meaningful.
If you wish to make your own system disk, you can either run the config program on the system disk (run LOAD P2 after booting GDOS) or load from plusd_system_tape.tzx, on either into your emulator or via Plus D or TZX loading device into your real Spectrum.
When it loads, you will be greeted with a garish rendition of Congratulations, which you can skip by holding down ENTER for a second. You will then receive guidance on how to answer the following questions. You can the format the disk if you choose, followed by copying over the system bootstrap and the config file updater. It would be a good idea to keep multiple copies of this disk image.
NOTE THAT FILES ARE WRITTEN IMMEDIATELY ON THE GOTEK BUT MUST BE SPECIFICALLY SAVED ON FUSE.
REFER TO THE MANUAL FOR FULL INSTRUCTIONS.
Spectrum Plus D v.23 Interface Downloads
- Plus D v2.3 Manual (PDF)
- System Software Tape (TZX)
- ROM file for emulators (ROM)
- Blank disk image (DSK)
- System with 1 drive disk image (DSK)
- System with 2 drives and printer disk image (DSK)
- All files with readme (ZIP)