Sinclair Interface

No mention of the Spectrum would be complete without looking at some of the technology that came alongside it. Out of the box, the Spectrum connected to the tape deck, power supply and TV. There was also a large edge connector (basically, the end of the circuit board). This edge connector was utilised for a number of items, some from Sinclair and many from other companies:

Interface 1 - By far the cleverer of the two. This provided 3 exciting interfaces:

1. RS232 serial port - this meant you could print to proper printers rather than just the Sinclair ZX Printer.

2. Network port - not quite what you might expect based on networks we have today. This worked at 100KB per second (most home users will be using wireless at 56MB per second (almost 1000 times quicker) and the computers needed to be no more than around 10 feet apart. Each end had to be told to send data or receive data though Sinclair had provided a program to send the same data to every computer listening and another so that a computer could listen to anyone sending and copy what was sent to the printer. I remember great excitement over this port though never saw it in use.

3. Microdrive port. It is probably difficult to describe a Microdrive now. Most people do not even have floppy drives in their computers. Imagine a program of less than 48KB (if you want to try this, you will have a file called ftp.exe in your system32 folder which is 42KB long), now save that file to your hard disk - if you watch very carefully you will just see the light flash! Now, if you have one, save it to a floppy disk and see it take just a few seconds. Much of that time is actually taken up with reading the index of the disk, finding a spare space, tracking the disk head to the right spot (the disk is 80 concentric tracks of information) then the computer has to wait for the right sector to come under the disk head and write the data. Quite a lot of activity for just a few seconds. Now lets step back in time to a Spectrum, you rummage through your tape draw for the one you want then insert it into your cassette recorder. Next you rewind the tape to the start (because you never remembered to do it when you finished last time) then press LOAD"" on the Spectrum then press play on the recorder and wait around 4 minutes. Most times you could then get started with whatever you had planned. You could get floppy disks in those days, these were 5 1/4 inches in diameter and could hold about 100KB. They actually were floppy as the square cover was flexible. The trouble was they cost a lot of money plus a lot more to buy an interface to plug between your Spectrum and the disk. I had one of these later on (prices fell and I earned more) but in the early days they were virtually unaffordable. Sinclair came up with a spectacular alternative in the Microdrive.

Interface 2 - This was much the simpler. This provided two joystick ports and a socket into which you could insert ROM-based software. ROM-based software meant instant loading and totally reliable but was more expensive to buy and impossible to copy (an awful lot of illegal copying went on with the Spectrum, all you had to do was connected the earphone output of one cassette deck to the microphone input of a second and mess around with the levels). Many other joystick interfaces were available though the "official" one was unusual in offering two sockets for two joysticks.

Microdrives take very small (44mm x 23mm) cartridges containing 5m of tape similar to that found in video recorders though just under 2mm wide. The tape was endless and the motor always runs forwards either at play/record speed or in search speed. The first sector of the tape contained the index. So, loading that game meant looking through a small drawer of microdrives, inserting it, loading the relevant file (as it could hold many files), the tape would then fast forward for the index section then read the index, then fast forward to the relevant point and then load the program. Tapes held 85KB of information, loading the index (or CAT - catalogue) of the tape took around 7 seconds (depending on where the tape was at the time) and 48KB would load in just 14 seconds or so. The Spectrum could be connected to up to 8 microdrives though 2 was more normal to permit copying. One problem was that the very thin tape stretched so the head could not read the data. This was easily fixed by reformatting the tape and re-saving things. Interestingly, as the tape stretched then you got more than 85KB of storage (as it was now longer) though, eventually (and all too soon) the tape either refused to read at all or snapped.