My system is a Nascom 1 with 64K RAM & Microsoft (ROM) basic
interpreter. I have recently found something funny and I don’t have any
explanation about a M.S.S. (Missing Star Screen) phenomenum. This little
program will show you the problem:
20 FOR Y=1 to 15
30 FOR X=1 to 48
40 SCREEN X, Y
50 PRINT "*";
60 NEXT X, Y
70 GOTO 10
This program is self explanatory but it does not work !
Philippe Wetterwald, France
(Ed. – It is all to do with the SCREEN command not resetting BASICs counter
for the number of characters in a line, so every so often BASIC says ‘Ah, time
for a line feed.’ Try setting WIDTH 255 to disable line feeds.)
ROM/RAM ZEAP, TAPES & DISKS
On page 28 of INMC80 issue 3 Mr. C. Bowden is having some problems
with running ROM ZEAP in RAM.
This is cured by replacing the contents of location D5F0 (which
normally contains the code INC (HL) with a hex 00 (code for NOP). This
disables the memory ‘test’ routine which arranges for ZEAP to crash when run
Of course, you may not like printing the above but I think that anyone
with the infinite intelligence required to get CP/M running should be able to
work it out in no more than 15 minutes.
On page 8 of INMC80 issue 4 Mr. R.S. Marshall writes about poor
quality recording tapes. I feel that the problem is basically two-fold: the
so-called ‘computer’ tapes (i.e. C12 long etc) are of lower quality than
practically any common audio tapes. Certainly their mechanics are very poor
and the only good reason for using them (rather than audio tapes) is their
lower price – if they work.
The other reason is that the data density at (say) 1200 baud is not
far from 1 bit/0.001" and most commonly used (i.e. cheap) cassette recorders
do not have their head azimuth adjusted to this degree of accuracy. If (as is
often the case) the tape is recorded on one machine and replayed on another,
then unless the heads of the two machines are identically set-up to within
0.0005" or better (over the tape width) the data will be unreadable. This
particular problem can be eliminated by replaying the tape (which was probably
recorded in stereo with the same data on both channels) on a stereo deck and
only connecting one channel.
I myself have been using TDK D-C60 & D-C90 tapes for about two years
and on average get about one error per several hours (yes) of playback time,
at 1200 baud. The deck is a Pioneer CT-200, costing about 85.00.
Regarding David Parkinson’s “1.5 Mbaud” article on page 41 (INMC80-4)
I would be very interested to hear more about his 8" Nascom disk system,
particularly how he wrote his BIOS. Also, does he still have working versions
of MOVCPM.COM and SYSGEN.COM? It seems to me that as soon as the BIOS is
modified (for 8" drives) then the standard MOVCPM cannot any longer relocate
the CP/M package for different system sizes. Also, which format did he chose?