MGT Plus D

This absolutely wonderful brilliantly useful piece of hardware (I like it!) consists of two devices - the actual +D interface and a disk-drive. The disk-drive can be almost any 'Shugart' standard type drive, but the one they supply with the interface (if bought with one) is a 3.5-inch Double Sided, Double Density(DSDD) type which can use both HD and DD disks in DD format.

That is not the only use either - the Plus D and the Disciple (its predecessor) both had Printer ports built in as well, so owners of the 48K machines without anything otherwise than resorting to a special interface such as the Interface 1 could still print out via a Centronics type connection to nearly all full-size printers.

OK, so what makes this so useful? Well, it allows you to store and retrieve (ie LOAD/SAVE) data to an industry-standard disk size rather than that 3-inch thing Amstrad used in the +3, and it does it rather well too, squeezing 780K out of a disk an IBM compatible would get 720K from. Most of the commands you could need are available to BASIC, using a special syntax which is usually of the form:

<command> d<drive>"filename" <type> although with LOAD and VERIFY there is a shorter syntax of the form:

LOAD p<no>

where <no> is the number that appears beside the file in a catalogue and determines its position in the CAT. 'no' is from 1 to 80. So 'LOAD p1' will load the 'first' file on the disk, although really it is only the one that has its header information at the first sector the +D looks at.

The drive number is either 1, 2 or *. 1 and 2 obviously mean disk drives 1 and 2 (if connected) and * means the last drive accessed.

Before using any DOS commands, you need to initialise, or BOOT, the DOS by typing 'RUN' (as in the microdrive fashion) to boot a disk, this means that the system looks for a file starting with "+SYS" on the disk and loads it if it's a CODE file, into the RAM area of the +D from 8192, 6656 bytes long. Until thats done, it won't do much.

You also need to FORMAT the blank disks before you can use them, just like any other operating system, and for a quick bit of technical information: The interface uses (for the default drive) 2 sides, 80 tracks per side (numbered 0-79, 128-207) with 10 sectors per side and 512 bytes per sector.

There are some different versions of G+DOS around, as the original is a bit buggy in places - don't try to resave a file with the same name unless its the only file on the disk as it tends to corrupt others for instance. There is, first step up "Thingi" which you need to provide an original G+DOS and it will modify, add a Multiface-like menu system to the snapshot button and POKEs, plus a RESTORE command to undelete files. But this still contains most of the problems.

The best one that I know of is a commercial alternative - BetaDos. This is very reliable, as far as I know no bugs at all, and adds extra facilities like being able to format a disk to more than the usual 80 directory entries. There are one or two programs it won't work with, but you can always revert back to G+DOS for those.

A more advanced, but virtually unheard of option, is to go for replacing the ROM as well as the bootable RAM which Uni-Dos does. This supports sub-directories, copying ALL file types, additions to the BASIC commands through a special file type. The problem is that
a) Its about 30GB pounds new;
b) As the ROM changes, even fewer programs will work with it (ie the clever ones!), and;
c) The quicker 'FORMAT' command means the MS-DOS utilities can't read them at all for transferring files to PC's :-(
I've actually got it though! It is quite useful when you need more than the 80 files-per-disk and filenames the same, as you can put them in directories.

Command is one of the following:

Also a selection of lower level commands are available to read and write individual sectors of the disk, open a channel to a file and various other useful things. One thing the +D does not support without modification, however, is sub-directories. Everything needs to be in the root directory so a maximum of 80 files per disk is the limit. You may say thats a lot, but trust me when using big 30-40k blocks of code with not much or big basic files, it does go quickly.

Wildcards are allowed, even in SAVE - but it's not a good idea to save a file with a filename something like "*temp" as it won't load without using <type> due to using wildcards in LOAD will load the first file it comes across matching that description in the catalogue.

There are two wildcard characters - * and ? which act in the same way as MS-DOS (but not the same as unix as a "*anything" will work under unix, but not using DOS or Spectrum +D. That is, * will match any number of characters of anything and ? matches a single character.

Printer commands are pretty similar to normal Spectrum prints - LLIST, LPRINT and COPY all work, and there are two different types of screen dump available. One good thing is that it is very flexible - lots of user-definable options for line-length, whether line-feeds are to be ignored or added, page-length, margin etc.


So, after all this some of you with real Speccies may be thinking "excellent" and possibly even "where can I get one?". Well, as far as I know (fairly certainly) they are not made new anymore so that means attempting to pick one up second hand. The original drive that the +D evolved from was the "Disciple", which is essentially the same except it's got a networking port and software which the +D doesn't. Some go for around 25 GB Pounds or so, so try not to spend much more than about 40.00 English pounds (GBP) at the most, depending on the condition.

I won't be held responsible for any problems, so follow this advice or whatever at your peril ok!

As my disclaimer states, I have no connections whatsoever to MGT who produce (or used to) the plus d interface.

I also reserve the right to be wrong... Please let me know if any of my informations are incorrect, but to my knowledge it should all be up to date. I also hope I have the right to reproduce this information. If not, apologies to whoever it's due and I'll withdraw it as soon as possible if you let me know.

Intro page
Spectrum Forever homepage
About me

File last updated: 21 May 1995

Author: John Garner / jmg7@ukc.ac.uk