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by Tilmann Reh and Jörg Linder
(The original article was published in 1995 in German in the KC-News magazine, the translation into English was done by Michael Scholz)
Many CP/M users have a strong desire to connect a harddisc to their systems. Unfortunately you have to have very in-depth knowledge about the system to establish an HD-interface. Coming up with a very particular solution Uwe Felgentreu uses special features of the KC system. This actually leads to incompatibilities with other systems.
Tilmann was looking for a solution that could incorporate in almost all CP/M computers. He found one and created the GIDE interface. A few prototypes have been built already and they are functioning well. Due to the lack of common interest a batch production hasn't been taken into consideration yet. But until now a growing number of people showed an interest in the GIDE interface so that first PCBs will be made in the near future.
The PCB's measures 60 mm x 75 mm. The board plugs directly into an existing Z80 socket. Therefore the Z80 is removed and replaced by the GIDE board. The GIDE board comes already with an Z80 CPU thus replacing the previoulsy installed one. In case this can't be done that way a ribbon cable connects the GIDE board with the system's CPU socket. Note, that the ribbon cable has to be kept as short as possible. Furthermore, a most recent design change enables you to add a real time clock (RTC) chip. This one can be battery backed-up using an external battery.
Concerned readers may now ask for the socket, meaning that there's no such thing in the D004 but the CPU has been soldered directly into the base PCB. Since a Z80 nowadays doesn't cost a fortune anymore the CPU's pins may be cut and (removed separately or left behind and) a matching socket may be soldered at them. This is to prevent the main PCB from being trashed by unexperienced 'craftsmen' in turn.
The interface is powered via the CPU socket. It consumes roughly 100 mA. It claims 11 I/O addresses (the base address is set up by adjusting 4 jumpers) and operates safely up to 6 MHz (or may be even beyond that). The D004 is clocked with 4 MHz and hence doesn't cause problems to the GIDE-IF.
The GIDE-I/F is hooked up to the system by updating the BIOS (refer to CPU280 as well). Systems which don't offer this chance due to the lack of availability of source code a resident driver has to be written. The code should be relocable and link into the BIOS jump table (can be done at almost no costs in CP/M 2.2). Any ideas and proposals regarding this are welcome and highly appreciated.
Since MicroDOS' source code will be available soon, the integration into the BIOS won't cause many problems. Tilmann will provide all (well documented) source code so that it is only up to our software experts to execute.
Sure enough, you wanna know what you would have to pay when ordering either the kit or the preassembled module. Recent calculations had us to come up with these prices:
Note: RTC denotes a Real Time Clock chip. Kit and preassembled module come with precision-made sockets.
In case you want to order the GIDE-IF you may want to talk to Jörg Linder. As soon as there's an adaption for the KC system available and initial testing has been done, available information will be provided in the 'KC-News'.