Software only an asterix away
A ROM extension board gives you the chance to add more than the
four possible language or utility ROMs to your BBC Micro. For
example, I have Beebcalc, Wordwise, CPN, Basic and the Watford
DFS chips.
There are ROMs available with Pascal, Logo, print and disc editing
utilities. And I hope more will follow. Certainly the BBC Micro
becomes very powerful with so much software only a * command away!
ROM extension boards are not easy to fit. Acorn have not socketed
the relevant chips (IC76 and IC20) and one must either desolder
the chip and put a socket on the board, or solder leads directly
to the chips
Though able to be done by a competent technician, my advice
is that this is a job for your dealer. The BBC board is delicate,
the chips close together and mistakes difficult to rectify.
There is another problem. Not all BBCs decode these ROMs in the
same way. In theory, the most right hand ROM socket has the highest
priority and as you progress towards the 0.1 or 1.2 OS ROM, the
priority gets less.
This was certainly not the case on my board. The ROM socket furthest
to the right had the highest priority, but after that it was a
little strange. Things were made worse when I fitted the ROM extension
board.
This is important because different ROMs can take priority over
each other and must sit in the right priority socket. For instance,
if you have two DFS chips fitted it is the highest priority DFS
that handles all default filing and so on.
If, like me, you have the CPN ROM but usually want Basic first,
then the priority order must reflect your wishes.
The highest priority is ROM 15. You can detect which ROM socket
your machine thinks it is accessing by the following:
Type into the machine:
*FX 252,0
Return
Break
Then reset the machine with CTRL + Break and change the 0 after
the comma to another number from one to 15. Repeat this until
you have tracked your ROMs.
When you press Break after the *FX 252 call, the machine "bombs"
into the ROM whose number you have specified.
The Technomatics board slots into the most right hand ROM position.
It sits just under the keyboard and across the top of the under-board
connectors. Thus it can keep as cool as possible.
Other extension boards tend to move into the heart of the micro
and can get very hot indeed, which may cause problems later.
The board is well made, adequately insulated from any other electrical
components with some of the best quality sockets I have found
on a low cost commercial board. This is important if you are continually
going to take ROMs in and out of your sockets.
The board has been sitting in my micro for a month now. After
the initial pangs of fitting, it has performed welt. But along
with the Z80 card and other additions, my BBC Micro can get quite
hot. This has led to inadequacies in the 6522 chip servicing the
keyboard being shown up
I understand this may be a far more common problem than yet
has come to light. After a few hours of operation either the keyboard
will not respond or certain keys behave strangely. Like all good
bugs it is rare, random and a devil to trace.
If you do lit additional boards then be aware that, though the
BBC power supply is more than adequate, some chips on the hoard
are very sensitive to temperature. You may think that your micro
is cool - but it isn't!
It will be a difficult choice between the Technomatics and Watford
extension boards. On "pence per ROM" Watford wins, but your board
is more likely to heat up.
I prefer to play it safer with the Technomatics hoard. The choice
is yours.
Ian Murray
