This meant that most programs would run alright, but as Mastermind and
Lollipop Lady both pick up data from the V.D.U. ram, this data would be
read as incorrect even though it would be printed correctly on the
After purchasing a new 2102 memory chip and fitting this in place of
the existing IC20 all my troubles were over. Incidentally this fault
also produces errors on the “L” command.
As “Doctor Dark” states in Issue 4 – just because the bit isn’t
displayed it still matters.
Thanks anyway for your help.
Many thanks for INMC News – keep up the good work!
An addendum to the “Memory Plague” report – I hit a couple of memory
problems with the STATIC memories. First was a 2708 which “flipped
bits” when it got warm, changing say 5A to DA in the Load program.
Second was a 2102 which started to output a few bits of its own about
20 minutes after switchon. The result in my case was continuous
printing of a random character. Changing this chip for one in the VDU
RAM position gave a regular pattern of dots on the screen when the chip
Both faults took ages to track down, as the whole system worked fine
from cold; trouble shooting tool which finally solved the problem? –
the wife’s hair dryer! The bright lads at Nascom were right about the
2708 but way off the beam on possible causes of continuous printing.
Moral, keep changing the chips around – I had changed just about
everything on the board except the RAM, as it worked perfectly in the
As a paid up member, I would like to praise the very worthy efforts of
the committee in producing the INMC News. Every issue a gem and this is
encouraging more people to contribute, even me. I must admit to mixed