Problems with SYS
Various problems have been reported by users of SYS, and most of these have
been cleared up very easily. For example you should not try to run a Gemini
computer using a SYS generated for a Nascom. It may be helpful to list a few
problems which people have encountered which have proved to not be errors in SYS.
When a Nascom with SYS is switched on and SYS is executed the system may
stop and wait for an input character before the configuration messages are
displayed. This is caused by a simple hardware problem. The serial input port has
supplied a spurious null on power-up which has activated screen edit mode. The
solution is either to assemble SYS with the SKBD option set to FALSE, or connect
the serial input line to ground so that no character is received. Remember that
the serial input may be set to RS232 or cassette, and ground the appropriate
When spurious input characters appear on the screen there are several likely
reasons. Check that the GEMINI flag is set correctly, and check the SKBD, NKBD,
GKBD and VKBD options carefully. GKBD must be FALSE with the Gemini GM813, as
there is no keyboard port. If you have a Gemini video card it is best to plug the
keyboard into it and set VKBD to TRUE.
If the system crashes when SYS is executed then it may be configured
incorrectly. For example it may specify a virtual disk when none is attached.
Alternatively there may be insufficient memory for the SYS BIOS if the correct
changes to MOVCPM have not been made (see above).
If a virtual disk is used and a different configuration of SYS is executed,
then the directory of the virtual disk may become corrupt. The system should be
switched off and on again to be certain of clearing this problem. This is because
cold boot does not clear the contents of the virtual disk, if it appears to be
I hope that you continue to enjoy using SYS. I have to admit, as Gemini
point out, that it is really only suitable for computing enthusiasts, but that is
who it was written for. Finally, my thanks to David Parkinson and Gemini for
their help with the inclusion of the standard disk software.
Please direct any queries about SYS to the supplier, as I only have time
to look into any really difficult problems, as with luck there aren’t too many
As the Gemini Winchester drivers have been incorporated with the kind
permission of Gemini, it has been agreed that the version of SYS incorporating
the Winchester drivers will only be supplied if the user produces evidence of
owning a Gemini GM835 Winchester. This is unfortunate for those who have the odd
Winnie knocking about in the junk box and wish to put it into use. On the other
hand, it does allow those who already have a Gemini GM809/GM815 system running on
a Nascom and who wish to add a Gemini GM835 to do so without scrapping the whole
system and starting again. On the whole, Gemini’s wish to protect their software
SYS is available from HENRY’S RADIO, see their ad. in this issue.
VIRTUAL DISKS – ARE THEY USELESS?
by RICHARD BEAL
Are virtual disks a useful invention or are they a desperate attempt to find
a use for lots of RAM? A virtual disk, also known as a memory disk or pseudo
disk, is a way of using a large quantity of RAM as if it is a real disk. In CP/M
terms the translation of track and sector to a memory address in the extra paged
RAM is done by special code in the BIOS.