Gepard – Part Five a): The Hardware, Phase 1

As I said the Gepard is a modular computer. Modular here means modular like in the early days of private computers: you have a case with a backplane, and everything else, from the CPU to the RAM, comes in single cards that can be inserted into the case. This is a photo of a typical Gepard configuration from the back. Yes, there are no card covers or handles, this is the factory view:

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Every Gepard computer had at least three types of cards in it: CPU, RAM, and Boot ROMs.

First Phase: 1984-1986, Gepards using Apple IIs or C64 as terminals and drives

In this phase, a Gepard had to connect to an Apple II or (later) to a C64 as there were no graphics cards, keyboard interfaces, or floppy disk interfaces yet. Instead, a Gepard I/O card connected to an Apple II card (or, later on, the user port of a C64) via a ribbon cable. The Apple II (or …) provided the keyboard, the display, and the floppy disk drive. Software, therefore, had to be booted from an Apple II floppy disk. There was some boot ROM on the I/O card specific to the computer model (Apple II or C64) it booted from. A program on the Apple II provided the necessary support to the entire operation.

The Gepard bus has the mechanical format of the ECB Bus (96 pins in 3 rows), but has a proprietary assignment of signals. It is a 16-bit bus basically giving you the signals of the Motorola 68000 CPU.

The hardware from the first phase could also be used in later phases.

backplane

Backplane
The backplane has 16 slots, the left 9 ones are quite close to each other while the right 7 are spaced further apart. One slot (the leftmost one) is used by the terminator card.

Terminator Card
The terminator card terminates all bus signals.

Case
The case is a very rugged, heavy, modular steel sheet thing. There is place in the front for the power supply (on the left if you look from the front), and for up to 2 floppy disk drives (on the right). The back half of the case contains the backplane, and the space for the cards. Each card can be inserted on two plastic rails, one on the top and one on the bottom.

The thick front plate has the power switch on the left. The front plate has no inscription. Sometimes, there is a “Gepard” sticker on the top left side. Later front plate issues can have either a lock on the bottom left side or a keyboard interface in the bottom right.

The case has a timeless sandish (the brochure calls it “light ivory” like the typical taxis in Germany) color with brown bezels at the front and at the back. The middle stripe along the sides is of the same brown color.

Typically, there is no back plate. Normally, you see the single cards in the back directly.

The front feet can be raised, giving it the feel of a measurement device.

Power Supply (NMC 101 S)
Input: 220V, 50 Hz using a German “Schuko” plug
Output: 5 V/6A, 12V/2A, -12V/1A
There is a quite quiet fan cooling the power supply.

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CPU Card
The first CPU card sports a Motorola 68000 with 10 MHz. Remember that in 1984 Macintosh has only 7.8 MHz, 1986 an Atari ST has 8 Mhz, and the Amiga has 7.2 MHz…
All Gepard CPU cards have a reset button.

ram.jpg

RAM card
There is a 128 kB DRAM card capable of running at 8MHz (-5%). You can have up to 7 of these cards in a Gepard.

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I/O Card
The is the Gepard end of the connection to an Apple II. It contains 2 boot EPROMS and an interface for a cable to the Apple II card.

Apple II card
This is the Apple II end of the connection to the Gepard. The connection is done via a ribbon cable and is an 8-bit bi-directional bus.

Complete Kits
A first phase Gepard kit either consisted of a backplane, terminator card, CPU card, RAM card, I/O card, and the Apple II card, or it included also a case and a power supply.

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