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 I1C37 and I1C38. 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 (2), 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 £FCOO 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


This is an OCR’d version of the scanned page and likely contains recognition errors.











Page 5 of 55