While reading the
latest 1984 issue
of this rag, i.e. June 1978, I stumbled upon an
advert for the Microcode BP14C 14-slot Backplane.
Succumbing to the blurb in the advert, I ordered one, pronto. A few days later, back
came the goods – in a BIG box. Actually, the only thing bigger than this
board is its price tag (67 quid).
To get the board to fit into my case (hand-built out of ex-county-council
plywood) I had to lose one of the board slots. I tell you folks, I cried.
After paying out 67 quid for the thing, here I was lopping an inch off the end
with a rusty hack-saw! Now, onto the board itself. The board is of a very
high standard (it should be for the price), measures 15″ by 8″ and is 2.5 mm
thick. The board is covered on both sides with green solder resist (I do hear
that Chris Blackmore is having one custom-built with blue solder resist to
board which is,
so I’ve been told, really amazingly blue.....).
The sheer thickness of the board may cause a few problems to the unwary
as the pins on the standard 77-way 80-BUS edge connectors just barely emerge
from t’other side of the board for soldering. This fact hit me for six as the
pins of the edge conectors on my old Vero motherboad were cut short so’s they
wouldn’t touch anything nasty, like the mains input plug. So, after forking
out all that bread buying the new motherboard I had to spend another 25 notes
on five new edge connectors. After splashing out close on £100 on a new
backplane with five edge connectors, guess what? My Nascom still does the
odd, un-programmed action. Ah well, that’s progress, I suppose!
And now a word for all those die-hards, who, like me, intend to use the
Microcode backplane with a Nascom-1.
As most owners of expanded N-1‘s know, the Nascom buffer board has a
ribbon cable sticking out of its component side which connects said board to
the 43-way edge connector on the N-1 board. The layout of the buffer board is
such that the best way of mounting it in the system is with its component side
facing the Nascom’s component side (motherboard driven from the left-hand
One of the main features of the Microcode backplane is that it terminates
all active 80-BUS signals into balanced RC filter networks. These filter
networks have to placed as far as possible from the CPU board in order to
function properly, i.e. the buffer board plugs into the backplane at the end
opposite the end containing the filter networks.
Now, as with most things to do with computers, it’s at this point that
all the fun begins. The tracks of the Microcode backplane are laid out in
such a way that when the buffer board is plugged into it, the ribbon cable on
the buffer board faces AWAY from the Nascom board. To overcome this problem,
I re-soldered the ribbon cable onto the solder side of the board so that it
again faced the Nascom board. Owing to this piece of board surgery, the
ribbon cable also needs to be twisted through 180 degrees so that the 43-way
edge connector mates with the Nascom board.
Although the Microcode backplane is of a high standard and works like a
dream, I don’t think it’s worth the 67 quid I paid for it. You pays yer money
and yer takes yer choice .....