80-Bus News


September–October 1983 · Volume 2 · Issue 5

Page 41 of 67

many double density machines is 48 tracks per inch, it is apparent that if the Micropolis drives were arranged to double step, then the data could be read. This of course would require software patches in the low level disk primitives in the Gemini BIOS which would not be the easiest thing to undertake but not outside the scope of many proficient machine code programmers. Note that Gemini are not likely to provide support for this sort thing unless demand warrants it, but it might be worth asking if only to indicate that the demand existed.

Powering up

The Galaxy 2 auto boots on power up when a system disk is inserted in drive A, an almost foolproof idea accompanied by a flashing instruction, displayed in inverse video, on the monitor which says ‘Insert disk in drive A’. Should the disk system fail to boot because a disk with no system or incorrect system was inserted, then a message to that effect is displayed. If a correct disk is inserted and the system fails to boot then it is possible to cause the Galaxy to revert to the very simple internal ROM monitor which is capable of carrying out diagnostic procedures. Only the bare essentials of the diagnostics are covered in the manual and for more sophisticated checks it is necessary to revert to the individual card manuals which are available from Gemini as an optional extra. In any event, unless the user has a very thorough working knowledge of the internals of the machine, he would be advised to consult Gemini through their country wide dealer network if problems are encountered.

Video Output

Computers of modular design are often associated with separate terminals as display devices, not so with the Galaxy. A separate card takes care of the video and feeds its output to the back panel socket for connection direct to a standard monitor display. The 25 line by 80 column display is to professional standards and the video card contains within its command set a sub-set which emulates the Lear Siegler ADM-3A terminal. However, whilst the Lear Siegler terminal is a serial device and hence somewhat slow, the video card plugs straight on to the system bus and is commendably fast. One reason for the choice of the Lear Siegler instruction sub-set is that much popular CP/M software is designed for use with this particular terminal and very little, if any, patching is usually required. However, the video card improves on the Lear Siegler instruction set in many ways, and much proprietary software can be further improved as regards speed by the incorporation of the extended commands of the video card. The video card also features a user programmable character set and also limited 160 by 75 pixel graphics.

The Galaxy is supplied with a standard monitor, the Phoenix P12, a 12″ green or amber screen monitor of Italian origin. Unlike the Galaxy, this has a plastic case, in a colour which matches the colour scheme of the Galaxy. The Phoenix monitor has logic rather than analogue inputs and is therefore free from that faint patterning which often accompanies analogue monitors although this was just discernable when displaying inverse video. The monitor was extremely sharp to the edges and almost free of picture ‘breathing’ when switching rapidly from normal to inverse video. Picture geometry was excellent. When supplied the monitor picture was a little undersize and slightly to one side. Not many users would notice this, although it is easily adjusted if required.

Page 41 of 67