Scor­pio News


January–March 1987 – Volume 1. Issue 1.

Page 37 of 63

start. And who is going to pay for component procurement, and a ‘get you going’ service after it’s built? No there’s nothing in it for a potential manufacturer – believe me, if there were, they’d have done it long ago.

So the final answer is to ‘do it oneself’, where the cost of the time taken to achieve an end it not considered as a material part of the costs. If I considered the cost of the time which I have spent in designing one off projects for my own use I would never have started them in the first place. Certainly if someone offered me one of my one off projects at a realistic price I would have certainly done without and not bought it.

I don’t consider myself as an unusually mercenary individual but I do like some (token) reward for my efforts, and in that I don’t consider myself unusual. Many things ace undertaken for the pleasure in doing them (I don’t write for this mag for the money, I’ll never get rich that way) and the rewards need not be monetary. But I personally think that your MOCSAN appears to represent very considerable amount of hard work and if it is to contain ULAs, then also prohibitively expensive, certainly not something to be undertaken for fun. If it isn’t fun, then someone (or many) will expect to get paid, and the projected price will go out of the window. No sorry Sir, it’s a nice idea, but to me, it’s not on. Perhaps I’am a minority, I’d welcome other views.

D. R. Hunt
(Reply written May 1986, re-edited Dec 1986)

A Review of the 2MB Upgrade for the GM833

by D. Greenfield

The Gemini GM833 Virtual disk board has proved very useful for over two years. When this board was first used, it seemed that it would never become full. Could it be that software is more sophisticated, or is it just less efficient ? Anyhow, “Disk Full” or “Write Error Drive M” started to rear its ugly head.

It seems that a virtual disk drive must have at least the capacity of a floppy disc on the system. Preferably it should have a lot more, at least 50% more as a lot of temporary files are produced during working.

The PBM upgrade for the Gemini GM833 board was fitted to the CM833 in about an hour. This upgrades the GM833 to 2MBytes, 4 times its original capacity. The Kit comes as a small pcd, wire, 41256 memory ICs, instructions and double sided sticky tape to hold the small Pcb to the main board. Everything went well on the modification, the instructions were reasonable, although an actual photo of the board would make component location easier. No tracks are cut, thank goodness. 8 wires are used to connect the pcb to the main board at various points. Pin 1 of all the memory ICs were connected together. This provides the extra address line required.

Everything seemed fine, on startup, the M> prompt displayed as usual. Running “STAT” displayed “2024K Bytes Free”. However, on loading more than 512K, the system failed. It seemed that the same 512K was “reflected” 4 times on the board. A phone call to PBH syetems threw light on the problem, two of the solder pins had bridged with solder under the board. Removing this fault resulted in correct opteration. The board has been running correctly since.

To conclude, the board represents good value. With care of soldering, the mod is easy to implement.

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