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Spectrum 128K Versions
The Spectrum
128 board was not by any means a
radical resign - much of it was very similar to the earlier
Issue 5. The big differences were in the number of chips (significantly
increased - many more memory chips plus an AY-3-8912A sound
chip in place of the old buzzer), the new ROM and the new
RGB, keypad and MIDI out connectivity.
As with
the earlier issue 3, the redesigned ROM caused major compatibility
problems, breaking many old programs. Some (notably Elite)
were reissued in 128K-compatible versions but for the most
part 128K owners had to put up with the situation. The problem
recurred repeatedly in the following years as new 128K designs
were produced.
Sinclair's tradition of incremental
design was dispensed with when, in 1986, Amstrad took over
the company's computer business. Externally, Amstrad's Spectrum
+2 was radically different to
any of its predecessors. There were major changes internally
as well.
The circuit board was completely
redesigned with around a new Amstrad ROM (as usual, this caused
some compatibility problems). Although the input/output sockets
were much the same as on the Spectrum 128, a major change
to the circuitry was occasioned by the addition of a built-in
cassette recorder, controlled by a second circuit board housed
to the right of the main board.
The Spectrum +3
saw further radical changes. The number of chips was drastically
reduced, with the rows of 8K memory chips familiar from previous
boards reduced to just two 64K chips. On the right of the
case, a 3" floppy disk drive was provided for mass storage.
Yet another new ROM was introduced to provide the machine
with a built-in disk operating system but, as usual, compatibility
problems resulted.
The last version of the Spectrum
was the Spectrum +2A of 1988.
As the name suggests, this was a variant of the Spectrum +2.
It was easily distinguishable from its older counterpart by
its black (rather than grey) case. Its innards, too, were
very different - the +2A was essentially a +3 without the
built-in floppy disk drive.
© Chris Owen 1994-2003
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