The Coupé could support two 3.5” Ultraslim Citizen Double Density drives each with their own WD-1770-02 disc controller allowing both drives to operate independently.
Unformatted capacity 1Mbyte, when formatted with Samdos as double sided, 80 track per side, 10 sectors per track, to the IBM 3740 standard gives 800kB with 780kB usable after directory space subtracted.
Having the drive controller within the drive housing meant that the floppy drive connectors could be used for other devices, most notably the ATOM IDE interface and the Sam Internal Parallel Interface SIPI.
When the rights passed to West Coast Computers the Citizen drives were no longer available so modified PC drives were used instead requiring a large cut out of the front of a blanking plate. They also sold kits for additional drives made in this fashion called Project 94A.
Connections to the two drives are made via two 32-pin Euroconnectors, with rows A and B connected. Drive 1 (DS0) is on the left of the machine and drive 2 (DS1) on the right. A list of signals available at these sockets are shown below.
|12A||5 VOLTS||12B||8 MHz|
|14A||5 VOLTS||14B||No connection|
|16A||5 VOLTS||16B||DS0 (wired to DS0 in left hand bay, DS1 in right hand bay)|
With age the drive belt can stretch, break or even turn into a gelatinous mess depending on it’s composition.
A suitable replacement belt is a 71mm diameter flat belt 2.8mm high and 0.6mm thick although there have been reports of mixed reliability.
To replace the belt you must remove the drive from its plastic shell, unscrew the metal shield and the motor to get access to the drive flywheel.
Clean the drive thoroughly to remove dust and fluff from the unit, clean the edges of the flywheel, jockey wheel and the motor spindle with a suitable cleaner on a cotton bud - also check the drive head worm gear for fluff build up and re-grease if required.
Take the opportunity to clean the drive heads using isopropyl alcohol and a foam/chamois bud (not cotton), and clean the skid plate under the head assembly.
Fitting the belt can be done without having to remove the drive cage if you have two pairs of tweezers to hold the belt:
With the drive slot facing you:
- Place the belt around the flywheel.
- Using one pair of tweezers grip the belt about 10mm from the loose end so that it forms a small loop and bring the left side of the belt around the outside and under the silver jockey wheel and to the right hand side towards the right of the post so that they come almost together.
- Bring the loop to the hole below where the motor spindle sits.
- Bring the other pair of tweezers up through the hole and grip the belt loop.
- Whilst holding the loop, drop the motor back into position, guiding the motors pulley through the loop you are holding, push the loop up as you bring the motor down and it should hook on.
- Screw the motor back down.
With age it has been noted that the service mount capacitors on the Citizen drives can fail and/or start leaking causing the drive to fail to read/write/format.
As with all capacitor leaks it is essential that the units are replaced and the corrosive electrolyte is removed before it damages the PCB, plus with surface mounts it is often hard to see if they have leaked under the cans but a dull patch or dulled solder points are often an indicator of this.
Presumably, three editions of the user’s guide were published. The 3rd edition can be found as a PDF Manual Scan at www.samcoupe-pro-dos.co.uk
Your Sinclair Rage Hard, (Recovered) courtesy of the YS Rock 'n' Roll Years YS52
Following fast on the heels of last month's SAM Coupe review, here comes the SAM disk drive and DOS; Sean Kelly gets out his trusty screwdriver and has a good poke.
The SAM disk drive is the first chunk of extra hardware to arrive for the Coupe, and as such helps give the computer a degree of sophistication not usually associated with things like the Speccy. Anyone who's used the drives on Atari STs, Amigas and the like will know what a boon a good, modern internal drive can be, and it should be exactly the same with the SAM. The difference is that these drives aren't actually an integral part of the computer at all, but very clever external fittings that only look as if they've been attached to the Coupe for life! They come separately, which means that you can buy the basic computer which loads games and other programs through an external tape deck (as you do with most Speccies) until you're feeling flush enough to splash out on a disk drive or two. Happily, MGT has made the units impressively slim and stuck two purpose-built holes in the front of the computer casing, so these extra add-ons slot in neatly and unobtrusively.
Fitting The Bits
Much to my surprise, actually attaching the drive is dead easy. Even those with as little computer assembly experience as me (ie zilch) should find it fairly straightforward. All you need to do is remove the little plastic cover on the front of the Coupe and shove the disk drive into the hole until it locks. You then turn the SAM upsidedown and bung a couple of screws in underneath to hold it in place.
The instructions are more than adequate (it literally took about three minutes) and the end results look surprisingly good. The SAM still seems a bit like a breeze '. block with a keyboard, but now it's a breeze block with a keyboard and a couple of nifty blue slot things on the front. Infinitely preferable. It adds nothing to the size of the computer, and with two drives fitted is a lot less awkward and space-consuming than either the ST or Amiga with a second drive (which comes as a bulky external unit). Of course, that's not really of much relevance to most people, but it does indicate how well thought-out the project is.
Like the 16-bit computers, the SAM uses the (now pretty common) 3.5 inch disks, which when formatted will give a total of 780K per disk - enough room to back up 16 48K games onto one disk! With the Coupe disk drive you not only get to keep your back collection of Speccy games but you get to load them a lot faster and easier too.
Next you need to load in the DOS (Disk Operating System) disk. Unfortunately, at the moment there's a slight prob with the DOS and the ROM of the Coupe, which results in the computer failing to recognise the DOS and throwing up an Error message on the screen. The manuals on the first batch of computers shipped out contain an extra bit of paper explaining the problem and giving simple instructions for fixing it, but later models will come with a slightly rewritten DOS so everything should work properly.
Basically, when the Error screen does show you simply need to call up the DOS by using the basic command CALL 229385. Unfortunately, although no functions are lost, all the pretty front-end intro stuff (like a decent menu display and so forth) seems to have gone missing, so the presentation is a bit basic and functional. In fact, it's much like the PC's MS-DOS in presentation and operation (if anyone's familiar with that). Commands are typed in, so there's no 16-bit-style mouse-driven icon laziness here (although a mouse does come later). The user manual gives an adequate guide to loading, copying and saving with the drive, but it certainly doesn't address itself to the more technical aspects of disk use.
Most of the commands are straightforward enough though, but I do have one quibble. The wildcard function is, if anything, a little too powerful. For example, a command like ERASE "N" will delete all files beginning with the letter N, which makes it a little easy to wipe away vital files without thinking. It could be argued that deleting unnecessary files can be avoided by simply being more specific in the deleting process (for example by typing ERASE "NORMAN" or whatever) but I'm sure that most computer users, being such lazy oiks, tend to use the shorter (but more dangerous) deleting procedure. I certainly did, until I lost a (luckily non-important) file by mistake.
Like the previous MGT Speccy drives, the Sam Coupe has a function which allows Speccy 48K games to be dumped onto disk in a fairly straight-forward manner. Unfortunately, I couldn't get this function to operate on our prerelease version although l am assured by MGT that the one you buy in the shops will work fine. The Coupe drive can also read disks which were written on the other MGT drives, so those owning a DISCIPLE or Plus D drive will be able to use their disks with the Coupe in the Speccy emulation mode. Unfortunately, these disks can only be read - they can't be written to or altered in any way. Presumably, though, those splashing out on two drives will be able to copy them onto a Coupe format disk.
And The Verdict?
The SAM disk drive will retail at £89.95, which will give the two a combined price of just under £260. Considering you could pick up a basic ST for around the same amount, suddenly the SAM doesn't look such great value anymore. Still, there's no reason why you should have to buy them together. You could quite easily soldier on with your Speccy cassette deck until such time as you're feeling a little more flush (or a birthday comes along, whichever is sooner). It's almost inevitable that once you've got your Coupe you'll want to pick up a drive sooner or later, and we can see no conceivable reason why not - it's a neat, slim unit, with bags of potential, and the speed with which it loads games, compared to the Speccy, is truly a joy to behold. Bravo
There is a bug that can cause disc corruption if a disc is left in the drive and the reset button pressed, see Hardware Bugs