While internet was celebrating the 30th anniversary of the Sinclair ZX Spectrum, I remembered where all my passion begun. It was at school, 1982, a professor and his personal ZX81. Wow!
The ZX81 came with 1 kB of on-board memory that could be expanded externally to 16 kB. Its single circuit board is housed inside a wedge-shaped plastic case measuring 167 millimetres (6.6 in) deep by 40 millimetres (1.6 in) high. The memory is provided by either a single 4118 (1024 bit × 8) or two 2114 (1024 bit × 4) RAM chips. There are only three other chips on board: a 3.5 MHz Z80A 8-bit microprocessor from Nippon Electric (now NEC), anuncommitted logic array (ULA) chip from Ferranti and a 8 kB ROM providing a simple BASIC interpreter. The entire machine weighs just 350 grams (12 oz).[5] The memory can be expanded externally to a maximum of 16 kB. Early versions of the external cartridge contained 15 kB of memory using an assortment of memory chips, while later versions contained 16 kB of chips but the lowest addressed kilobyte was disabled.
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