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The Sinclair ZX81

Here it is, my first computer !

Looking far sleeker than the ZX80, the black ZX81 really looked the part.

Shown alongside is the Sinclair RAM memory expansion pack which expanded the memory to a huge 16KBytes ! The RAM pack plugged into the rear of the ZX81 and connected to the Z80 bus. It had the unfortunate habit of "wobbling" when the keys were pressed which meant that you lost any unsaved work.

A number of other companies produced a range of memory expansion modules, one of these was Memotech who went on to produce their own range of computers - the MTX series (the real focus of this website). The Memotech RAM packs made a much more secure connection to ZX81 and did not suffer the infuriating "wobble" of the Sinclair models. See here for more details about the Memotech expansion packs.

Like the ZX80, the ZX81 was available either as a self build kit or preassembled, most buyers, including me, opted for the ready built unit.

Specifications

Processor  Zilog Z80A
Clock Speed  3.25 MHz
ROM  8 KBytes
RAM - fitted  1 KBytes
RAM - maximum  64 KBytes (external expansion), 56KBytes useable
Display  24 lines of 32 characters per line
Colours  Monochrome
Sound  None
I/O Capability  Z80 Bus, RF Out (TV), Cassette Interface
Data Storage  Cassette Tape
Built in languages  Sinclair BASIC

See how Sinclair BASIC compared against competitor machines of the time when running PCW Benchmark tests here.

Launch price (kit / built) 49.95 / 69.95

The ZX81 BASIC Manual in HTML format, from ZX81kit.com,  is available here.

You can also read it online from the Old Computers website using this link.

Sadly, I no longer have a ZX81 - I sold it just after I bought my ZX Spectrum. For those of you that does have one, you may find that getting a decent picture on a modern TV is somewhat problematic, if so, you may find this page useful, it gives a brief description of the possible problems and offer a solution in the form of a modification to the ZX81 RF Modulator - ZXVid.

I have started to gather ZX81 items though, I think that I should try to get hold of an example of the Memotech ZX81 add-ons to complete my collection of Memotech hardware.

There is a wealth of information available on the internet which describes the ZX81. Check out the sites below for more information :-

Planet Sinclair Covers the full range of products from Clive Sinclair, including the ZX range of computers, including the ZX81
Wikipedia ZX81 Entry on Wikipedia
Build a ZX80/81 Grant Searle's pages on how to build your own ZX80 or ZX81 from scratch
ZX Software UK Tony Barnett's store information for Sinclair ZX computers
Old Computers Website dedicated to, yes, old computers
   
   

 

 

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