The NEC V20 and V30 Processors
Readers of this magazine and its illustrious predecessor will know of my
pre-occupation with benchmarks (groans from Chris Blackmore), a state of affairs
which has arisen mainly because I do a lot of number-crunching as part of my
Those lucky people who purchased the GM888 boards which Scorpio were offering
at a very reasonable price (or the less lucky ones who already had them at the full
price) will have noticed that there is an 8088-2 processor and next to it an unused
40 pin DIL socket for the horrendously expensive 8087-2 co-processor. The latter
device will set you back something like £150 but is a tremendous help if the CP/M-86
version of your favourite language supports it.
The NEC V-series of processors were introduced a few years ago and two of them
will be of interest to readers. The V20 (correctly described as the uPD70108) is an
8088 pin-compatible with a considerably extended instruction set (including 80186
instructions and 8080
emulator mode); the V30 (uPD70116) is a pin-compatible
replacement for the 8086 (as used in true 16-bit micros such as the Amstrad PC)
and has the same, extended instruction set and emulator mode of the V20.
I have been using both chips – the (8/16 bit) V20 in my GM888 board and the (true
16 bit) V30 in the Amstrad – for several months now and I have been very pleased
with the improvement in performance they have brought to both systems. With the
V30, the improvement is a decrease of just over 50% on timings of a wide range of
programs. Because of the 8 bit bus on the GM888, the improvement in speed is less
marked, but averages out at about 12% on the mix of programs that I tend to use.
This is due in large measure to the way in which the arithmetic instructions are
coded in the NEC chips and there would be little advantage in using one of these
in a system which was, for example, used primarily for word-processing.
Currently (December 1987), the chips are available from Technomatic Ltd.
(__ ___ ____) at £10 + VAT – a great deal cheaper than anywhere else. You need
the 8MHz versions – V20-8 or V30-8. Technomatic do a very rapid mail order
(credit cards etc.), but if you are in the Edgware Road area, looking at the
well-known shop where Dave Hunt used to disseminate pearls of wisdom, Gemini
boards etc., it is worth calling in at no. 305 where Technomatic have a shop (close
your eyes if you don’t like Beebs).
If you really want an 8087, which will speed up your programs by 2 – 20 times
(depending upon the amount of floating point maths involved), Technomatic are