ITT 2020 Computer - Apple II Clone
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The ITT 2020 was the first Apple II clone, manufactured by ITT in the UK under license from Apple Computer, specifically for the European market. In the United Kingdom, it was distributed by Microsense Computer Limited. In the Benelux, it was distributed by Bell Telephone mfg. company. The ITT 2020 was released in 1979 but was only manufactured for a few years.
The major difference, and the reason ITT believed this personal computer would be a success, was that the colour video signal conformed to the European PAL standard, rather than the American NTSC standard. This meant colour graphics could be viewed using a standard European monitor or TV set, rather than having to import an NTSC monitor from America or Japan as was the case with the Apple II.
The most significant other change was the hi-res graphics resolution. ITT increased the horizontal resolution from the 280 pixels the Apple II Plus used, to 360 pixels. The vertical resolution however, remained the same. This made many Apple II programs incompatible with this computer. The higher resolution was a necessary consequence of the higher frequency of the PAL colour subcarrier. In order to provide enough bits to the video shift register to generate the higher PAL subcarrier frequency, 9 bits per memory location were needed, rather than the 7 bits the Apple II+ used. To achieve this, an extra 16Kx1 memory chip was added to the motherboard, which added a 9th bit to the Hires memory pages (0x2000 to 0x5FFF). This made it necessary to modify the graphics routines in Apple's Applesoft Basic interpreter in ROM. To emphasise this difference, ITT called this "PALSOFT". To make room for the longer graphics routines (manipulating the 9th bit required extra code), the HPLOT instruction was limited to a single parameter, rather than a string of parameters.
ITT also supplied a floppy disk drive that was identical to the Apple II disk drive with 13 sectors and DOS 3.2. They never supplied the upgrade to 16 sectors and DOS.
Some brief information regarding the manufacture of the computer was provided to us by Alan Campion in 2016:
'The ITT2020 that's in your collection almost certainly passed through my hands, because at the time I worked for the ITT Consumer Products division at Basildon, where they were assembled, and I was tasked with overseeing that. As well as myself, the team consisted of one test technician, and about 16-20 female assemblers, occupying one small corner of the factory. The rest of the factory was given over to churning out TV's. As well as the UK, some of our production also found its way to Germany.'
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This exhibit has a reference ID of CH31495. Please quote this reference ID in any communication with the Centre for Computing History.
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