Rage Hard!

Rage Hard!

Phil South looks at the ultimate deterrent in the RAM pack wobble stakes, as MGT launches the TwoFace, a switchable two-way user port.

Phil South

A what? A switchable interface for my user port? Why would I want one of those?" I said. MGT smiled at me and said, "Try it." Oh well, I'm game for a laugh, so I tried it. To my great surprise, I liked it, and found it more useful than many other things I've shoved into my user port. Fnar!
    Expansion ports have been popular for years, allowing the industrious Speccy user to connect as many gadgets as he likes to his machine, all at once. But such ports have always been fraught with problems. In most cases they're just a piece of ribbon cable which has been soldered with a spare male connector in the centre. I've used a lot of these jury rigged ribbon style connectors in my time, and they've always been wobbly, unreliable, and had a nasty tendency towards crashing. And the most perilous kinds of connection are those which involve the dreaded PRINTER INTERFACES!!! How many times have you wanted to print something out from your Speccy and found that the port is gummed up with the very item you want to print from?

Dr Snouty's Casebook
Take the VTX5000. A fine little modem, and very inexpensive to buy. But what do you do if you want to print out your screens of Prestel/Micronet? It seems like a fairly simple process. You save your screens to tape online, and print them out offline when the modem's detached from your user port. Or so you'd have thought. But in order to recall the screens from tape, you have to have the modem attached. Why? 'Cos the screens are in a special format, peculiar to Prestel, and won't load in a naked Spectrum.
    Okay, so you wedge your printer interface into your user port, then the lead from the modem. But the modem sits under the Spectrum, raising the interface off the ground and makes it wobble. The computer crashes. So you get smart and lay your modem upside down, BEHIND the Spectrum, so everything's in contact with the table. But it still doesn't work. You unplug everything, plug it back together... and so on.
    This all sounds pretty stupid, but it often happens. A dodgy lead trashed my Speccy, and it was all down to the jolly old 56 way connectors which are the only way the Speccy can communicate with outside peripherals.
    That's where the TwoFace comes in. You can connect your peripherals, like the Plus D disk interface, printer, Vidi ZX, whatever, to your ports, and either switch them in one at a time, or all together. This is an excellent idea from my point of view, as not only will it allow me hours of trouble-free computing, it'll stop me drop kicking the little fiend through the window! Anyroad, before I get carried away, let me tell you all about the physical construction of the device.

So, What's In It?
The construction of the device is very neat. No floating circuit boards, no messy wires whizzing around all over the shop. Just neat and tidy little ICs nestling on a few solidly fixed Printed Circuit Boards (PCBs).
    The chips are what you'd expect from a device of this type, especially one with a Kempston compatible joystick port wedged on the side. On the secondary PCB are the three chips, A 74LS240 Octal Buffer, a 74LS32 Quad 2-input OR Gate, and a 74LS138 3-Line to 8-Line Decoder. These chips do two jobs. Firstly they wire in a joystick into the user port, and secondly, they make sure that you can switch the IORQ and MREQ without causing any hardware headaches.
    The only other bits inside the box are a 9-way right angle male D Connector (joystick port to you) a 4-pole 3-position slide switch, and the three PCBs, including 2 X male and 1 X female 54-way connectors and a metal casing. Four rubber feet on the bottom of the unit keep it at the same level as the user port on the Spectrum. The unit rests very comfortably behind the Spectrum, and is as sturdy and wobble-free a unit as I've ever lobbed onto my user port. It's stability comes from the metal casing, plus its grippy rubber feet, which hold the surface of the table so well, that for a minute I thought it was stuck to it!

Yes, But What's It Like!
The TwoFace works well. The select switch on the top means you can have either both ports in use at once, just the back one, or just the front one. And the best thing about the TwoFace is that because it's only switching the IO and Memory Request lines, you can usually fit incompatible interfaces to it with absolutely no hassle - no crashing and no chip rupture. And even if they are incompatible, you have the choice to switch them in or out to your own requirements.
    Being able to use a Kempston joystick at any time is good news too, as most joystick ports are a bit tricky to use in conjunction with anything else. Another nice feature for +D users is the little gizmo that comes free with the TwoFace called a 'wobble plate'. Sounds like a serving of jelly to me, but in fact it's a small piece of metal which screws into the TwoFace, and also into the +D in the upright position. This means the two units are as one, and every time you press the snapshot button, you get a lovely picture of your screen, not a busted Spectrum. Yes folks, you can say bye to the wobble. Now then, I wonder if MGT could do the same for my tummy...

FAX BOX
Gear - MGT TwoFace
Price - £16.95
Supplier - Miles Gordon Technology

Many thanks to Alan Maxwell for typing this up

Rage Hard! pages on this site

1988 36

1989 38 39 47

1990 51 52 55 57

1991 61

Published in the December 1988 issue of Your Sinclair

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