INMC 80 News


October–December 1981, Issue 5

Page 67 of 71

that works, but the problem recurs, replace the rectifier. I know of one case where the rectifier was replaced by a 6 amp rated device, which was bolted to the case. The connections were made from the P.C. Board in heavy wire. No further problems occurred on either of the machines I know of that could be attributed to the P.S.U.

Has anyone heard of the National Semiconductor MM58174 Microprocessor Compatible Real Time Clock? This is a very neat 16 pin i.c. which costs about 10.00 (depending where you buy it). It requires a 38768Hz clock from a crystal controlled oscillator. It can run in power down mode as low as 2.2V, and keeps a track of time from 1/10 sec to leap years! It offers the option of interrups on 0.5 sec, 5.0 sec, 60 sec. Would any highly intelligent person who has designed a circuit for this to run on a Nascom like to send me a copy?

I would like to thank the people who wrote to me with information about the IBM33FD floppy disks. The day they start to run is coming nearer. I intend, subject to changing my mind about the matter, to drive them from an input/​output board, having cunningly substituted an SIO for the PIO. Beware!! The SIO is not pin-compatible, and an adapter is necessary. Also the SIO does not calculate the CRC with the correct initialisation to give IBM 3740 standard, so disks recorded in this way are system dependant. However doing it this way will allow me to see if there is any point in going further with these disk units, or if I throw them away (having first removed the stepper motors for a plotter) and buy some real 8″ Shugarts or Qumes. Should this method of driving them work, in spite of being system dependent, I intend to build a Z80 based disk controller, which will be intelligent enough to handle the spooling of data to a printer, and perhaps even tape input and output. I’ve recently acquired an NCR 6000 baud tape unit, which is also intelligent I’ m now using the term very loosely!

Nascom’s BOOBS (or why are there no lady Nascomers?)

My reference to the method of checking the capture range of this Cottis/​Blandford interface was in error. The correct date was the December 1978 P.C.W.

The reference to the A.C.C. newsletter should have been to Vol 6, No.5.

Who did it?

It would give me, and I’m sure many other Nascomers, the greatest satisfaction to hear that the **** who designed (“designed”? Daddy, Daddy, I thought you said it was **** . Ouch, oh!) the Famous Nascom series A RAM board had been shot at dawn, without benefit of a) a blindfold, b) a final cigarette. If I knew his name, I could label my picture of Hitler with it, and throw darts at it.

Teletype Printer mechanism (no keyboard).
Working but very noisy 35.00 o.n.o. 041.942.2482

Nascom 1, Nas Sys 3, and Buffer Board 95.00 or will sell separately.
Ring 041.332.3841

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