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1980s Computers Explanation of terms

The ZX Spectrum 128

ZX Spectrum 128K


Sinclair Research Ltd (UK)


Spectrum 128

Date Launched

February 1986



Microprocessor type

Zilog Z8400A (A CMOS Z80A) @ 3.5 MHz

ROM size

32 kilobytes

Standard RAM

128 kilobytes
(104 KB available to user, rest used to store a copy of the operating system)

Maximum RAM

128 kilobytes

Keyboard type

Separate moving keys pressing onto a touch sensitive membrane

Supplied language

Selectable standard Sinclair BASIC (as used on the Spectrum 48K) or extended Sinclair BASIC 128K with additional commands for sound control and for a RAM disk.

Text resolution

32 X 24 characters

Graphics resolution

256 x 192 pixels.

Colours available

8, each at two brightness levels


3 channels, output through TV speaker.

Cassette load speed

1500 baud

Special features

Could operate in 48K mode allowing it to run most existing Spectrum software.
Single key entry of BASIC commands in 48K mode, or by typing them in full in 128K mode.

Good points

Corrected many of the limitations of the original 48K ZX Spectrum:

  • Gave a steadier TV display
  • Had a proper sound chip
  • Had over twice as much RAM, accessible through bank switching

Bad points

Cost £50 more than the current Spectrum Plus.
Not compatible with all Spectrum software and add-ons.

How successful?

Did not offer existing Spectrum owners a compelling reason to upgrade and by 1986 the basic design of the Spectrum was outdated.
The Spectrum 128 was withdrawn in late 1986 when Amstrad took over Sinclair's computer business.


The Spectrum 128 was in fact designed by Sinclair's Spanish distributor, Investronica.
It was launched in Spain towards the end of 1985 but in the UK Sinclair had a deal with Dixons (one of their largest retailers) that they would not launch any new model of the Spectrum until stocks of the old model had been sold.
The result was that the Spectrum 128 did not go on sale in the UK until February 1986 and it thus missed the large Christmas market.

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