The NEC V20 and V30 Processors

by P.D.Coker

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 research.

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