The ITT 2020 was an Apple II computer clone manufactured by ITT under license from Apple Computer (the first licensed clone), specifically for the European market. In the Benelux, it was distributed by International Bell Telephone Company. It was distributed in the United Kingdom by Microsense Computer Limited.
The major difference, and the reason ITT believed this personal computer would be a success, was that the color video signal conformed to the European PAL standard, rather than the American NTSC standard. This meant color 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 for the Apple II. ITT sold this computer for a few years, starting in 1979. When Apple Computer started shipping the Apple II Europlus, ITT withdrew from the market, although the Europlus did not support color.
ITT also supplied a 113.75 kB single-sided floppy disk drive that was identical to the Apple II disk drive, supporting 13 sectors under DOS 3.2 on a floppy disk. They never supplied the upgraded 140 kB single-sided double density drive supporting 16 sectors under DOS 3.3.
Other changes
A Power Supply manufactured by ITT themselves
The case was spray-painted a matte silver color, and the keyboard was black. The ITT 2020 used a higher clock frequency, necessary for the PAL signal. A crystal was used (Four times the PAL subcarrier frequency of ), whereas the Apple II used a crystal- four times the NTSC subcarrier frequency of . In the ITT 2020, the crystal frequency was divided by 17 to give the microprocessor a clock frequency of . In the Apple II, the frequency was divided by 14 to give a microprocessor clock frequency of . The slots in the back of the casing were smaller, making it extremely difficult to install some expansion cards. On later versions of the ITT2020, the reset switch only worked in combination with the Control key. This was done to avoid the many accidental resets earlier (and Apple II) users complained about. The 4th annunciator output was not supported. The I/O addresses ( and ) Apple used for this output were used by ITT to bank-switch the extra RAM chip. The third button on the game connector was not supported, as ITT used the I/O address of this input () to read the extra RAM. The bug in the routine in the Apple II that required users to a patch, was resolved in the ITT 2020. Some users reported a bug in the routine, causing strange shapes to appear under certain circumstances. The DOS ITT supplied with the 2020 was Apple DOS 3.2. However, a catalog listing showed Basic programs as type 'P' (for PALSoft) rather than type 'A' (for Applesoft)
Consequences
Any Apple II program using graphics had problems on the ITT 2020. Only programs written specifically for the ITT 2020 could make proper use of the Hi-res graphics, with horizontal co-ordinates of up to 359, rather than the 279 maximum of the Apple II
If the program used the Applesoft Basic graphic commands in ROM, the image would appear squashed- circles would appear as ellipses and squares as rectangles. If the program accessed the video memory directly (and many did, for faster performance), 40 white or black vertical lines would appear through the image due to the 9th bit not being set. Programs using the HPLOT command with multiple parameters did not work properly. The colors were different to those on the Apple II in both hi-res and lo-res modes. In lo-res mode, some colors were not available. Programs using the missing annunciator output or missing switch input did not work. Because of the difference in clock frequency, programs on the ITT 2020 (without graphics) ran 2% faster (benchmark tests confirmed this). Programs that automatically loaded the patch for the ONERR GOTO bug would crash if an error occurred, as this bug was already fixed. Programs making system calls to subroutines in ROM would sometimes crash because some entry points had changed. BSAVE and BLOAD of graphics images did not work, as the 9th bit was not included in the file. The Hi-res routines in Apple's Programmers Aid did not work. The different timing signals made some peripherals and expansion cards malfunction.
ITT eventually released a technical note with an assembly language program that allowed users to load and save hi-res images.
Graphics
Differences with the Apple II
The most significant difference between the ITT 2020 and the Apple II is the Hi-res graphics resolution. ITT increased the horizontal resolution from the 280 pixels the Apple II used, to 360 pixels. The vertical resolution however, remained the same. This made many Apple II programs incompatible with this computer.