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
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
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