80-Bus News

  

November–December 1984, Volume 3, Issue 6











Page 5 of 55











POLYDOS ROMs at D000H-D7FFH with the links at LKS1 placing MROM, VRAM and BROM as normal. Pin 10 for D000H-DFFFH is connected to both pin 7 (XROM) for the POLYDOS ROMs and pin 4 (BLOCK A) for the RAM chips in sockets IC37 and IC38. This all worked with a 64K Gemini RAM Card until the AVC was installed. The memory card was amended as the AVC manual demanded but I did nothing to the N2. As a result (?), there is a gap in memory from D8000H-DFFFH. I suspect /RAMDIS is the culprit but am not sure how to use the advice in the AVC manual to recover the lost RAM. Eventually, I want to use the spare parallel ports on the Gemini GM816 (see below) to handle this linking – then I could switch ROM BASIC in or out.

I am sorry about the delay in returning the Questionnaire, but writing letters to the Tax Inspector and even editors of computer journals comes a long way after programming. Specific answers to most of the questions are appended to this letter. In general terms I very much enjoy reading 80-BUS News (though inclined at times to mutter about too much of the software stuff being CP/M orientated) but am becoming alarmed at the numbers of Nascoms now on the second-hand market.

Disloyal it might seem, but I have acquired a Sinclair QL so that I can get my hands on something closer to a proper operating system and am now setting up an RS232 link to the Nascom using a Gemini GM816 and a GM818. Does this make the QL an expensive printer buffer or the Nascom an extremely expensive disk drive?

Yours truly, C J Cave, South Croydon, Surrey

Reading the small print

Reaction to layout of Dave Hunt’s ramblings, 80-BUS News, Vol 3 – Iss 3:– “Aaarrrggghh!”. Frantic scrabble for magnifying glass. This layout is not a good idea. Reducing the number of pages is also not a good idea. We don’t want a return to INMC Issue 1. Besides, how would you have room to publish the design of my 80-BUS Orgone Accumulator, if you cut down the length of the magazine.

The 80-BUS News has cost £1.50 since January 1982. This is £9.00 a year. I must have spent quite a bit more than £300 on my beloved Uriah in the past year. Compared to this expense, £9 for 6 issues of 60-odd pages of information, including reviews of hardware and software (which could well prevent a costly mistake) is nothing. As even 2000AD has had its price put up by 20% in the past year, are all the 80-BUS freaks out there REALLY too stingy to shell out a few extra quid?

I have been trying for more than a year to start a tape circle, but none of my offers have yet been published in the 80-BUS News. How do you expect us “dodos” to be anything else if you suppress us?

Yours truly, Kevin Wood, Canterbury, Kent

80-BUS & BBCs

About Mr Young, the person who wishes to attach a BBC to the 80-BUS (what a repulsive thought!). What does he mean by the 1 MHz tube?

There is a thing called the 1 MHz bus. This buffers the lower 8 bits of the address bus out of the BBC and the data bus bi-directionally. There are also two select signals provided (which each map the bus onto one page of memory, from £FC00 to £D00), reset, the Read/​Write line, a 1 MHz clock and an interrupt line. There is also an input to the BBC’s internal amplifier (which is responsible for the “frying eggs” sound of the BBC). The 1 MHz bus is totally putrid.

There is also a thing called “The Tube”. This is even more putrid, and is smothered in registered trade mark signs, although why anyone would want to












Page 5 of 55