Introducing the Sinclair Spectrum +3

Up until the takeover of Sinclair by Amstrad the design was a little dated despite the revamped 128 and clearly something had to be done. Wisely Amstrad decided to get a machine on the market pronto and the new grey cased +2 was moreorless the old 128 with a decent keyboard and built-in tape deck. The machine was a success. With money in the bank there was the opportunity to upgrade it and in this Amstrad succeeded very well to produce a decent machine that everyone had been clamouring for over the years although it has to be said that it isn't perfect but a reasonable compromise.

There were several packs produced including a light gun and software pack in a large flash box. Alternatively you'll get a +2 sized box containing the +3, power supply the size and weight of a house brick, TV cable and a manual. You may also get a joystick but definitely no introductory disk so don't bother looking for it.

The good news first of all is that the computer is now BLACK in colour. Much more like a Sinclair machine and it actually looks quite nice. Second piece of good news is that it has a disk drive built-in (hurrah!). How long have we wanted this in a Spectrum? Up until now we had to rely on other companies to produce them. The bad news is that it is a 3 inch disk drive although it does maintain compatibility with the CPC and PCW ranges. The +3 can even read PCW disks.

The manual is up to Amstrad's usual excellent standard and contains much valuable information and examples. The section on programming in BASIC is as good as the early Sinclair 48k manual and has some of the old examples in it. The section on the +3DOS is equally informative and even has some assembler examples.

More bad news. The +3 is incompatible with many software titles especially games. Even some written for the +2 won't run. Ho hum. Luckily most software was rewritten and is marked as suitable for the +3. And software houses produced heaps of software on disk which ensured compatibilty.

Now a lot has been written about 3 inch disks, none of it particularly glowing but I rather like them. They are reversible so both sides of the disk can be accessed by a single sided drive provided it is flipped over first. They are reasonably fast and the drives are relatively smooth and quiet. They are prone to failure however although most of the trouble stems from a dirty head (which can be cleaned) and a worn drive belt which can be replaced.

+3DOS does support double sided drives in 720k format but you'll need 3rd party software to format it and you're still restricted to 64 files in total, the same as on the PCW so a second drive is useful. The snag is that the CPC 664 cable comes with a huge interface containing the drive controller although the CPC 6128 cable should fit.

There is a parallel printer port which needs a special cable - the CPC 6128 cable does the job perfectly if you can find one. The normal ZX printer output is sent to the parallel port for transmission to a printer which works exceedingly well.

The expansion port however may give trouble as the essential 9 volt line has been removed thus rendering old peripherals inoperative. I imagine this was done to prevent easy transfer from tape to disk thus ensuring good sales of new software on three inch disk. However a thing called THE FIXER was invented by MGT who have since disappeared. This reinstated the 9 volt supply (I've no idea how) thus enabling the use of old peripherals. And besides a new +3 version of the Multiface unit by Romantic Robot enabled transfer from tape to disk. These are no longer available and difficult to find secondhand.

The RS232/MIDI port servives but still retains the peculiar plug of the older machines. The keypad plug is now renamed AUX but can no longer drive a keypad as all the software has been removed which means that the old trick of accessing these extra commands from the keyboard using graphics mode will now not work which is a pity as it made using the editor much easier. Incidentally, all the old Sinclair commands to do with the RAMDisk (CAT! for example) have also been removed. The AUX port remains to be used with a light gun. Joystick ports are still wired to use on Amstrad joysticks although adapters were supplied with most compatible joysticks by other manufacturers.

The TV port remains the same as does the RGB monitor output. The tape input socket is wired differently from previous machines and needs a special cable (see NewsCall above).

That accounts for external changes. What about inside. There is a totally new motherboard design to accomodate the new disk drive (the later +2A motherboard is NOT the same as the +3 and cannot accomodate a disk drive). The ROM is now held on two 32k chips which are switchable from software. The keyboard is attached to the upper casing and is attached by two cable connectors that pull out from connectors embedded on the board. There is also a cable connecting the 'power on' LED to the board. There are fewer memory chips than on the old 128 (just two) but the sound chip remains the same.

Problems

The machine is plagued with one or two problems. RF output interferes with most electrical equipment including televisions. Sound output is awful unlike the crystal clear 128 output. Transferring tape to disk is difficult without extra hardware. External 3.5 inch drives (if fitted) are restricted to 173k per disk (you can't swop them over like a 3 incher) but they are cheaper. The casing creaks and feels very cheap. The keyboard is useable but not brilliant. Like I said, it's not perfect.

+3DOS

The new DOS to control the disk drive (and the RAMDISK) is held in ROM and switched in to page 7 of memory thus taking up a sizeable chunk of the RAMDISK. The old 128 and grey +2 had around 64k of RAM available as a RAMdisk but the +3 has only 58k because of the space taken up by the DOS and a cache for the disk drive. The black +2A has no need to set aside memory for a cache for the disk drive so there is around 62k available according to the manual although I've not had the opportunity to test this. I have yet to discover whether a +2A can drive an external disk drive.

The new +3 DOS is very like CP/M in character and has been designed with compatibility with the PCW range and CP/M itself with lesser compatibility with the CPC range. PCW disks can be read and written to directly which is very good news if you happen to own CP/M for the +3 or a PCW machine as well. The +3DOS fulfils all the criteria required in as much as it can copy and erase and list files but the commands it uses are somewhat non-standard. What appears to have happened is that the existing Sinclair BASIC commands have been enhanced for use with the disk drive which presumably has kept the size of ROM required to a minimum.

The unfortunate side effect has been to produce a rather confusing set of commands for those familiar with Sinclair BASIC and all commands need to be enclosed in quotes. However it only takes a little time to get used to and they do all make perfect sense. For instance, to print to the printer under MSDOS you use the command:-

copy filename.txt prn

which means copy the named file to the printer. Under +3Dos use:-

copy "filename.txt" to lprint

Similarly a file can be copied to the screen using:

copy "filename.txt" to screen$

which puts a file to the screen. You may recognise Sinclair keywords COPY (normally used to print a copy of the screen), TO and SCREEN$. These keywords keep all their original meanings.

The disk drive works in ways one would expect. Accessing drive B: by flipping over the disk is prompted for. All commands can use wildcards and the commamd:-

erase "*.*"

ellicits a prompt asking if you really want to erase everything on the disk. The RAMdisk is accessed as drive M: (the same as the PCW) and is 58k in size. The disk drive is restricted to 64 files and even the smallest of files takes up at least 1k so the physical limit of 64 files is never reached on the RAM drive. The DOS can also only handle 2 disk drives which are both single sided low density (173k).

The DOS command departs from CP/M where listing files is concerned as the Sinclair command CAT is employed instead of DIR. The old 128 and +2 commands to do with the RAMdisk have been removed so CAT! won't work anymore. CAT does report file sizes as well as the space left on the disk which is very handy.

Loading from tape is still possible but only from inside +3 BASIC using the command:-

load"t:"

which will then load from tape. To go back to the disk drive substitute the t: for a:. To use the loader option from the main menu requires that a file is set up for it to find. Pressing RETURN on start up tell the machine to search for a file named DISK which will be a BASIC program telling it which file to run on disk. Empty commands like load"" won't load the first file on the disk. Programs can also be copied to RAMdisk and run from there if required. One quirk of the DISK program means that only a disk formatted under +3DOS (rather than CP/M) will work from the loader option. Obviously the two formats are not quite compatible in some way.

+3 DOS also contains several extras not found in CP/M. Writing to the disk with a filename that already exists will result in the existing file being renamed with the same name but a .BAK extension so ensuring that no data is accidentally lost. Also the FORMAT command will ask query continuing if the disk has data on it already. These are both very handy additions.

Because the RAMDisk is much larger under +3DOS than under CP/M I've tried copying CP/M files using +3DOS. On the whole this seems to work but has lead to some files being unreadable (particularly programs) when using them whilst running CP/M. I will investigate this further. Meantime keep backups of everything before attempting to use +3DOS for CP/M files.

One of the main problems is getting tape software to disk. It is possible without extra hardware or software but fiddly and not possible if turbo loaders are being used which limits it to older software much of which won't run on the +3. The CAT"T:" command will give useful information on files held on tape but cannot read headerless files. The only real solution is a MULTIFACE +3 which are rare to say the least.

Within the +3 ROM lies several programs designed to test new machines whilst they were still in the factory to ensure that at least all the machines that leave the factory worked properly. This quality control is something that was sadly lacking during the early days of the Spectrum's life.

These programs are accessed via peculiar key presses rather than directly from BASIC and should be used with the greatest of care so please read this entire section before trying it on your machine.

The one routine of all these that is detailed in the manual is the test card and is the easiest to obtain. Reset the computer to clear the memory. Hold the BREAK key and press the reset button then release the BREAK key. This will produce a display of columns in different colours with a steady beeping sound in evidence. If you have colour but no sound then try retuning the TV set and likewise if the colours are a bit grainy.

The most useful will carry out a series of tests. To use them first press reset to clear the memory. Hold the break key and press reset which will bring up the colour and sound test screen detailed in the manual. With the screen displaying the test card and still beeping, press the following keys simultaneously:-

Q A Z P L M

which are fairly easy to press as they are the keys down the left and right hand side of the keyboard. A set of brief instructions will appear warning that Disks will be corrupted if left in the drive whilst running the test. You will need a formatted but blank disk to test the drive.

There will then follow a series of tests. If any fail for whatever reason then extra test equipment will need to be used to obtain a diagnosis. The one useful test is the speed of the disk drive. However this was produced for a brand new drive so old drives will almost certaily fail. However if the figure obtained is greater than +1.0 then you may have a drive that may fail at a later date although it may only require a change of drive belt.

The least useful test displays the message:- "Hello there, I'm a +3" in Sinclair block graphics that flash. Quite what this is meant to achieve is anyone's guess. Select 128k BASIC and type the following:-

COPY RANDOMIZE

without a line number. Pressing RETURN will ellicit an error and it will bleep at you. The trick is to press RETURN and then the following keys very quickly:-

P L C Z

It's a little fiddly and takes a few attempts.

The final one converts sound to light presumably to test the tape deck on the +2a but it works with the +3. Select the test card as before and press the keys:-

A E U

A black screen signifies that the program is ready to go. Plug in a tape player and play a tape.

There is lots more to be said about the +3 but the manual says most of it so read it thoroughly but I hope I've given you an idea of what the +3 can offer.