When running a BASIC program, or even when pressing a key for any input, the display would, therefore, blank out momentarily while the processor was busy. As a result of this approach the ZX80 could only generate a picture when it was idle, i.e. This was an idea that was popularised by Don Lancaster in his 1978 book The TV Cheap Video Cookbook and his " TV Typewriter".
Ebay sinclair zx spectrum generator#
The video display generator of the ZX80 used minimal hardware plus a combination of software to generate a video signal. There were problems with durability, reliability and overheating (despite appearances, the black stripes visible on the top rear of the case are merely cosmetic, and are not ventilation slots).ĭisplay was over an RF connection to a household television, and simple offline program storage was possible using a cassette recorder. The machine was mounted in a small white plastic case, with a one-piece blue membrane keyboard on the front. BASIC commands were not entered by typing them out but were instead selected somewhat similarly to a programmable graphing calculator - each key had a few different functions selected by both context and modes as well as with the shift key. The ROM contained the Sinclair BASIC programming language, editor, and operating system. Both computers can be made by hobbyists using commercially available discrete logic chips or FPGAs.
Ebay sinclair zx spectrum upgrade#
However this was mainly a cost-reduction effort the hardware functionality and system programs were very similar, with the only significant difference being the NMI-generator necessary for slow mode in the ZX81 (see ZX81 for technical details), and the 4K integer-only Sinclair BASIC upgraded to 8K floating-point-capable, with the upgraded ROM also available as upgrade for the ZX80. The successor ZX81 used a semi-custom chip (a ULA or Uncommitted Logic Array) which combined the functions of much of the earlier hardware onto a single chip reducing the chip-count from 21 to 4. The ZX80 was designed around readily available TTL chips the only proprietary technology was the firmware. Internally, the machine was designed by Jim Westwood around a Z80 central processing unit with a clock speed of 3.25 MHz, and was equipped with 1 KB of static RAM and 4 KB of read-only memory (ROM). The ZX80 was named after the Z80 processor with the 'X' meaning "the mystery ingredient".
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