April/May 1980, Issue 7

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Just when I was beginning to wonder whether anyone was reading my articles, the INMC forwarded a letter to me from R.L.D. Boxwell. Master Boxwell, who is fourteen, has been trying out unknown opcodes, and has found a remarkable total of eighty-one of them, which I shall pass on now. Since (presumably) the Z80 chip is only tested for the instructions that appear in the book, they may not all work on your Nascom. He doesn’t count these in his total:

CB30   CB31   CB32   CB33   CB34   CB35   CB36   CB37

(Ok, everyone knows those are shift logical lefts gone wrong, but look at this lot!)

Now there are 75 codes there, all of which must have uses. Then we have:

The function of the following is not known, other than the fact that they definitely do something:

(Whoever gets the job of re-typing that lot has my sympathy, and if they get it all right they will also have my undying admiration!) (I’d rather have a drink, and give my NASPEN a rest! –Ed.)

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