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.
|| 3.25 MHz
|| 8 KBytes
|RAM - fitted
|| 1 KBytes
|RAM - maximum
|| 64 KBytes (external expansion),
|| 24 lines of 32 characters per line
|| Z80 Bus, RF Out (TV),
|| Cassette Tape
|Built in languages
|| Sinclair BASIC
See how Sinclair
BASIC compared against competitor machines of the time
when running PCW Benchmark tests
|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
Computers website using
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 -
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
There is a wealth of information available
on the internet which describes the ZX81. Check out the sites
below for more information :-