80-Bus Journal


Okt.​/​Nov.​/​Dezember 1984 · Ausgabe 4



*The Chipdisk*

a design of Dutch origin

From Holland information reached us that the test stage of the Chipdisk is closed and that the possibilities for commercial applications are being viewed. What are the advantages of this really revolutionary design with respect to existing equivalents such as e.g. the RAM­DISK or the Winchester drive?

To give some clearness about this a description of the system is necessary. The whole system consists of 4 parts of which a simple but amply measured 5 Volt power supply forms a part.

The following part is a number of 64 K-dynamic RAM boards connected to a eurobus. In this approach lies the flexibility of the system and a basic system only needs such a board. With an increasing need the Chipdisk can grow along in little steps from 64K to 1/2 Megabyte and with small adjustments even greater capacities are possible.

The third part of the design is an interface- board which buffers the eurobus signals and at the same time generates a number of extra control signals. The part discussed until now is assembled in a case and has the appearance of a diskdrive, entirely complete with power-on led and activity led. This case is connected by means of a 50 way flatcable with an I/O board in the host computer on which the processor signals are buffered and three I/O ports are decoded. The whole system gives the host computer only a load of three I/O ports, Through this the Chipdisk can in principle be used on every Z80, 8080, 8085, 8086 or 8088 system and in the future adaption for other processors is probably also possible.

The system which is finished now, has been designed for the Nascom Gemini 80 bus and it operates with 128K ram to great satisfaction. By making a clever use of modern IC’s the software interfacing is extremely simple and the Chipdisk reacts like a normal floppy disk drive with sectors of 128 bytes and tracks of 16 sectors. The number of tracks is dependent on the number of RAM boards and amounts to a multiple of 32.

The interfacing is extremely simple and for CP/M instant software is available while for other applications flow diagrams are available.

After this description of the system I shall now mention a number of advantages with regard to the systems mentioned before. The RAM­DISK such as many systems apply it. constitutes the system memory and is then addressed in page mode or via banking. These are often costly provisions which make a system for non-users of it unnecessarily expensive. The software for this is also very complicated and everything is system bound. Another possibility are instant I/O boards for a particular bussystem with certain great quantities of memory which are also systembound and often cost a great amount of money.

The advantage of the chipdisk is in this case the modular buildup so that one can start with a small and relatively cheap system. In comparison to the Winchester which couples great storage to high speed the Chipdisk is as regards the price per bit disadvantageous but the great vulnerability and the high purchase price of the Winchester drive are the reverse side of the medal. The hard- and software interfacing is much more complex too.

In the way of speed the Chipdisk is in all cases amply the winner and a speed gain with a factor 30 is with respects to a floppy no exception.

I do not wish to conceal a disadvantage of the Chipdisk either. It is clear that when the computer is switched off the data in the Chipdisk get lost, so that the results of an operation as the last stage must always be written to a real floppy.

The application of the Chipdisk therefore lies mainly in the realm of sorting, assembling, compiling and designing operating systems.

For further information about this new medium please you can apply to the designers of the Chipdisk.

H. Vermeulen,​H. Rietveld
_______________ __
Den Haag
Tel. ___-______

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