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- The ZX-spectrum was the successor of the ZX-81, there was a 16Kb and a 48 Kb model. The
16Kb was easy to upgrade to a 48Kb by inserting RAM chips.
- The keyboard was very unusual as with most Sinclair machines. The keys felt like
pressing on an eraser. Compared with the ZX-80 and ZX-81 it was a big improvement, but
there was no way you could type with 10 fingers. But for entering basic programs it was
all right, It took some time getting used to it. The keyboard has 40 keys every key had 5
different functions (these were printed on top, above and below the keys). To get to these
functions you had to press the key or symbol-shift+key or caps-shift symbol-shift and then
the key, or caps-shift symbol-shift and then symbol-shift+key. Then the basic command
jumped on to the screen.
It sounds quit complicated and if you had never done it before it was, but after a while
you could enter basic programs faster then if you could only type with 2 fingers.
- Screen:
- 32 characters, 24 rows every character is built up from a matrix of 8 by 8 pixels.
- graphics 256 x 192 pixels
- 6Kb RAM for video 768 bytes for attributes (colours, brightness, flashing)
There is a choice of 8 colours which can be made bright and flashing.
You can have 2 colours in a matrix of 8 x 8 pixels, these are called the ink and the
paper.
- interfaces:
- expansion bus
- UHF connector, (standard it was not possible to connect it to a RGB or a composite
monitor.
- In 1982 there were no 32 Kbit RAM chips available there were however 16Kbit and 64 Kbit,
Sinclair could use 3 banks of 8 "4116" RAM chips. But that would have been
too expensive, so instead he decided to use 8 rejected "4164" Ram Chips. Uncle
"Clive" Sinclair bought a very large quantity of rejected RAM chips. The fault
of these RAM chips was always in the same part of the chip and by only using the high or
the low part of the chip he created 32Kb RAM chips and that with the 16Kb already in the
machine added up to the total of 48Kb RAM. In the design of the motherboard you can
already see that this was the idea. With a wire bridge you can tell the computer to use
the high or the low part of the RAM chip.
Many of those RAM chips turned out to be 100% OK and some amateurs turned their machines
into 80Kb machines so they had another 32Kb more which they could use in assembler with
bank-switching method.
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