xw Advice on additional disk drives for the Spectrum +3 J. Elliott, 1993 ================================================================================ The Spectrum +3 comes supplied with one disk drive, built-in. This file contains information and advice about fitting a second ("B:") drive. There are two main options: 1) The Amstrad recommended 3" drive, referred to in chapter 10 of the manual. 2) A third party 3.5" drive. rThe Amstrad FD-1:u This is almost identical to the built-in ("A:") drive. It will interchange disks quite freely, but you can still only get 173k per side of a disk (192k with special format programs). It is quite rare nowadays, since 3" drives are obsolete. It will work happily with CP/M DISCKIT. rA third-party drive:u There are three main models: 1) CPC type external B:. An example is the GVL external CPC6128 B: drive. This particular drive can be used as a 2x192k drive, like the FD-1, or as a 784k double-density drive. The changeover is made by moving a switch on the back. 2) DATADUAL-8 by Pinboard Computers. This has a switch on the front which changes it between a 784k B: drive, a 2x192k A: drive and a 784k A: drive. It can be used to replace a failed A: drive. Note that it cannot be used as a 2x192k B: drive. See "Notes on 784k A: drives" below. 3) DATATWIN-8 by Pinboard. The top-of the range model, it has two drives. One is a replacement A: drive and the other is a B: drive. Switches on the rear allow you to choose between the drive in the +3 or the drives in the DATATWIN. The top drive can be a 2x192k A: drive or a 784k A: drive. The bottom drive is a 784k B: drive. See "Notes on 784k A: drives" below. rFormats:u Disks made by the +3DOS "FORMAT" command have 173k per side. 3.5" disks cannot be turned over but 2x192k drives have an extra switch to tell the drive which side of the disk to use. All 3.5" disks can hold up to 784k (this uses both sides of the disk at once), and +3DOS can use these formats. The problem is that it can't make them. Disk drives tend to come with utility disks allowing you to format disks to 720k or more, but these formatters will be for PCWs or CPCs. Unless you own a PCW or a CPC, the formatters will be useless. If you bought a CPC accessory, you will be confronted with a lot of text about "RamDos, RomDos, MS800" etc. pIGNORE ITq. The fact of the matter is that while CPCs can't really handle formats bigger than 192k without extra software, Spectrum +3s can. The only thing they can't do is format the discs. There is therefore on this disk a program: DU50. It is the same as the CP/M disk formatter DU49A.COM, but rewritten for the +3. It allows you to format disks to up to 784k, which +3DOS will recognise automatically afterwards. It can also format 3" disks up to 192k. DU50 is written in machine code, which is stored in the file: DU50.HED. It is essential to format with DU50 if the drive you are using is a "720k-only" version. You should turn the disc drive and the TV on before turning on the +3. Unfortunately this makes the disc drive rattle and emit peculiar noises; the solution I reached was to disconnect the TV aerial lead before turning on and only reconnecting when everything had warmed up. rSoftware:u If you get a CPC6128 B: drive, the documentation will tell you that special software is needed to use the drive with 784k disks. This is not true for the +3 which can recognise 784k disks automatically both in +3DOS and CP/M. The Pinboard drives have a "720k booting" option, allowing PCWs to boot from 720k 3.5" disks. This software should pNOTq be used on the +3. Instead, you should use P3MAKE (in this archive) which writes +3 boot sectors onto 720k discs. Recent Pinboard drives also come with 'FIB' files which allow PCWs to use the 3.5" drives at higher efficiency. These should not be used with the +3. Most programs should be able to recognise drive B:. An exception is Multiface 3, which always uses drive A:. Even if you copy M3 saved programs onto B:, the program (eg "GAME") will always try to load its code (eg "GAMEC") from A:. Some programs (eg PAW) should be set to use B: as a data drive (with PAW this is done with the Y menu). Others should just have B: put in front of the filename. rThe ABBA Switchu This is a little device which plugs into the back of the +3 and swaps the disc drives over (so that the built-in drive becomes drive B: and the external drive becomes drive A:). Again, it is designed for CPCs, so please note the following: 1. The second paragraph of the fitting instructions needs to be modified, since the +3 has a red lamp on top. Open the computer a little and you will see two wires running between top and bottom. At the bottom end they are connected to the circuit board by a small plug which should be disconnected. Remember to reconnect it when you reassemble. 2. When you are using the 3.5" drive as drive A:, the built-in disc drive will have its light permanently on. This is nothing to worry about. rNotes on 784k drive A:u +3DOS will work perfectly whether Drive A: is 784k or 192k. However, format programs (including the FORMAT command) find difficulty in re-formatting 3.5" discs from 784k to 173k. This will probably only apply for ABBA switch users. The program I use to perform this is Supersoft's "Disc Doctor", which has one very useful option to format 173k discs quickly without trying to read from the disc (which is what causes the problems). +3 CP/M will normally only boot from a 173k disc formatted with DISCKIT. The best way to do this is to format a new disc in the 3.5" A: drive under +3DOS and then use the command COPY "B:" TO "A:" with the CP/M master disc in the 3" drive and the new disc in the 3.5" drive. Once you have used a 720k or 784k disc in the 3.5" drive, you can't use any 192k or 173k discs in it until you reset the computer. It is possible to have +3 CP/M boot from a 720k disc - see P3MAKE.DOC. rOrdering:u When ordering, always state that you have a Spectrum +3, and send a photo- copy of pages 314-5 of the manual (describing the disk socket). Spectrum +3 drives MUST have an additional power supply. rSPEEDUPu If you are lucky enough to have twin 3©" drives, or if you are confident that you will not need to use the 3" drive until you next reset the computer, then you can run the program SPEEDUP on this disc. It sets both drives to the timing parameters for 3©" drives, so you pmust notq use the 3" drive after running SPEEDUP, until you reset the computer or run SLOWDOWN (the opposite program). The CP/M equivalents SPEEDUP.COM and SLOWDOWN.COM are also suplied. ______________________________________________________________________________