Posts Tagged ‘Gepard’

Gepard – Part Five a): The Hardware, Phase 2

November 21, 2019

In this phase, the Gepard becomes a self-contained, autonomous system as all necessary components are available from the Gepard manufacturer. This means text and graphics output, keyboard input, and floppy disk drives. The cards of the First Phase get improved or have successors, and new functionality is added in the form of cards. The second phase is coming to an end when the Gepard Computer GmbH closes.

Second Phase: 1984 – 1986, Gepards as autonomous computers

68010

CPU cards
Now a Motorola 68010 card (also at 10 MHz) is available, replacing the original 68000 card (at least in the Price List 1/86, the old CPU card is no longer available).

512

RAM cards
The first card was a 128 kB DRAM card. It is soon followed by a 512 kB DRAM card, and then by a 1MB one. There is not much to say about these cards apart from you can have up to 7 128 kB cards, or up to 2 512 kB cards, or multiple 1MB cards plus one 512 kB card.

80z

80 Characters card
This is the card used in text Gepards to display text. It can display (surprise, surprise) 80 by 25 characters. Each character consists of a 8 x 11 pixel grid. It can display four different, freely programmable fonts (a 128 charachters each) at the same time. The program to define these fonts is even contained in the Operating System. Additionally, it can display (equally monochromous) graphics with a 320 x 192 pixels resolution. This card can be used in parallel to a GDC graphics card. The standard output interface is a (Y) component cinch plug. The card can serve monitors with a line frequency of 15.75 KHz. The monitor options from the catalogue were a 12″ Taxan KX 1201 or Taxan KX 1203. Recently I had no problems displaying the output on a quite recent Sony 4K TV and an older noname CRT TV.

GDC Graphics card
The GDC graphics card (or, rather, subsystem) is architecturally a marvellous thing, but way too expensive. As it deserves an own blog entry, I will give it one :-).

fpdfpc

 

Floppy Disk system
Such a system consists of a Floppy Controller card and one or two, theoretically even up to four floppy disk drives. The controller card can control either two standard 3.5″ floppy drives or two 5.25″ ones, or up to four “Gepard” 3.5″ floppy disk drives. The data rate can be selected between 250 and 500 kbps. Drives can have up to 2 times 80 tracks. Software-wise a track is divided into 5 sectors of 1024 bytes each. This results in 800 kB disks capacity.
The “Gepard” drives are Sony MP-F52W models that have a data rate of 500 kbps, something the early Gepard newsletters are really excited about. In the first price list (1/85) a full height Sony drive is depicted, a year later the drive is half height. The controller card has two potentiometers with which the Read Pulse Width and the Read Pulse Width can be adjusted.

mfc

Multi-Function card
This cards contains a keyboard interface, a battery-buffered real-time clock, two joystick ports, a programable timer, a PIA, an analogue multiplexer, two D/A converters, and one A/D converter. It was the standard means to connect a keyboard, so these cards are often contained in 2nd Phase Gepards. The keyboard interface is a 5-prong (big) DIN connector. The standard keyboard was a Marquardt type 703 or 704 with a Gepard logo. Later on there was a cheaper option, the “AFC Operator” keyboard. The Multi-Function card was also the audio source and typically the (mono) loudspeaker contained in the computer case connected to the sum of the two D/A outputs. There was no sound chip, so one had to prepare the audio data digitally so it could be put to the D/A converters. There was a program for the Gepard that could play out sample libraries using this mechanism.

img_20181203_214128991.jpg

Parallel/Serial cards
The standard way to connect to a printer was the Parallel-Serial card. It provided two Centronics parallel interfaces and two RS232 serial interfaces. The card even came with a Centronics cable. Additionaly, there was also an 8*RS232c card. It had a massive 50-pin Sub-D jack which provided the 6 signals for the 8 connections.

sram

SRAM/EPROM card
This card has 8 sockets for SRAMs or EPROMS. The advantage of SRAMs is the faster access speed, the disadvantage the higher price. You can mix SRAM and EPROM, but you have to always use pairs of chips. EPROMS provide Read-only memory that is available without having to read it from a floppy disk.

Complete Kits
Also in this phase the kits from the first phase are still available. Additionally, there is now also the C64 version of the Apple II system. Then, there are two new kits. The first kit is the “Text Packet”: a complete Gepard system complete with case, power supply, keyboard, 80 characters card, floppy controller card, one 3.5″ floppy disk drive, a multi-function card, and the elements from the Apple II kit (except the Apple II card). The RAM card is 512 kB, and the I/O card is used as a Boot ROM card. The Text Packet (or variations of it) seems to be the most frequent Second Phase Gepard. And, finally, there is the “Graphics Packet”. It is a Text Packet kit plus a 14″ monochrome monitor and a GDC graphics card as well as a parallel/serial card. The RAM card has now a full MB.

Other cards
There are also a few other cards in the catalogue 1/86:

  • an 8-channel A/D and D/A converter card with 10 bit resolution
  • an 80-channel card with 40 output and 40 input TTL channels
  • a mouse/track ball card with two 9 pin interfaces
  • two MIDI interface cards. One with one MIDI input and one output interface, and one with 8(!) MIDI outputs and 8 MIDI inputs. The latter card even includes six serial ports
  • an IEEE-488 interface card

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

November 13, 2019

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:

img_20181203_213727159.jpg

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.

img_20181203_214846158.jpg

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.

io.jpg

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.

Gepard – Part Four: Known Gepard Computers

November 10, 2019

As there aren’t a lot of Gepard computers to start with and as I meet quite some of them I thought it might make sense to have a public directory of known Gepards. As not all of the owners (well, hardly any of them) have given me permission to do so, I’ll exclude personal details except the city and the configuration if known to me

City Configuration URL
Stuttgart Phase 1 + 3 GDC graphics https://randoc.wordpress.com/2019/11/03/gepard-an-early-german-68000-hobbyist-workstation/
near Stuttgart Phase 1
Hamburg Text Gepard Phase 2
Michelstadt 68020, 128kB Text Gepard
Clausthal-Zellerfeld 68020, 4MB, Text Gepard http://www.computersammler.de/umgelabelter-gepard-computer/
Mutlangen ???
Mutlangen ???
Schöneberg Text Gepard? http://kundenserver.computronics.de/vintagecomputing/Rechner/Gepard/gepard.html
Leimen ???
??? ??? ???

If you want to be on the list, send me photos of your Gepard computer.

Gepard – Part Three: Operating Gepards Today

November 10, 2019

Display

You can display something only if you have either a 80-Characters card (80-Zeichen-Karte) or a GDC graphics card. Gepards that connect to an Apple II or C64 get their output on their Apple II or C64 screen.

Both cards can connect at least to a single component (Y) output, often as a cinch plug, monochrome only. Fortunately, component-in can be found even today in high-quality LCD displays such as some TVs or computer displays. Component means YPbPr (or, to be more exact, the single Y plug of this interface), not RCA RGB nor anything you can get out of a VGA, DVI, oder HDMI interface.

The original monitors were black/green CRTs with a single component interface. If you have one of them, use them if they still work.

Keyboard

Tricky. The Gepard uses a keyboard with a standard serial interface. As far as I know, these are very hard to come by these days. I don’t think that any PC keyboard can be used.

However, the advantage of using a standard serial interface is that you should be able to use any terminal or computer with a terminal program. The plug is a 5-prong “DIN” interface. Pin 1 is Data In, Pin 2 is Ground, Pin 3 is Buffer Full, Pin 4 is +5V. If “Buffer Full” is logically 1, the Gepard can receive a new character.
The serial interface uses: 1200 bps, 8 bits data width, 1 stop bit, Even Parity

Operating System/ Software

This is something I can help with as long as you can use 3.5″ Floppy Disks. Simply email me and let’s see what I can copy.

Missing/Additional cards

You’re out of luck. Curently, I do not know any source for new cards. Ebay is always a possibility, but I have only once seen a Gepard on Ebay, and it was mine afterwards 🙂 Single cards are probably even more scarce, especially as it is hard to identify them.

Gepard – Part Two: My digital resources

November 5, 2019

I decided to start with my digital resources for download first, because it might interest some people. So, here are scanned price lists, newsletters, manuals and the like. Unfortunately for some, they are all written in German.

Price lists

Newsletters

Manuals

(1985) Manual 4.0

(1986) Manual 4.1

Others

Gepard – An early German 68000 hobbyist workstation

November 3, 2019

Part One: What’s that all about?

OLYMPUS DIGITAL CAMERA

First Generation Gepard (Front)

I did not write an entry for quite some time now. Not because I was lazy, but because I was busy with a single retro computer project for almost a year now. It started like so many of my blog texts: I bought something unusual on Ebay. Normally, I then start to research it on Google, maybe make a few photos – voila a new blog entry.

This time however, it was so rare and obscure that there weren’t even enough information to fill a small text. So, I had to go to a journey first finding people that knew people that knew something substantial. I had to actually go out and phone up people and ask whether they would send me information, lend me hardware, software, and documentation. I made an actual phone interview with one of the key people of the original manufacturer. I scanned a lot of paper. I drove away and got computer, monitors, and keyboards handed out. I felt like an actual (re-)discoverer of things, charting virtual landscapes noone ever entered (after the original natives have left it that is :-).

But enough of this banter, you want to know what this is all about. I give you: the mighty Gepard (Cheetah) computer, a mid-1980s, modular, German 68000 computer with a proprietary operating system written with a proprietary Modula-2 compiler developed from nerds for nerds. Only about 300 systems have been built originally, probably only a few of them survived, and even less are in an operational state. The documentation is exclusively German, and the computer pre-dates the Web. Apart from a new mentions in forum posts, it’s the first time that something will be written about it in English. Currently, no Computer Museum has a Gepard (as far as I am aware).

I plan to have a (short) series of entries treating different aspects of the Gepard:

At the Vintage Computer Festival Berlin (VCFB) 2019 I gave a presentation and I exhibited a working Gepard. I’m afraid the presentation was given in German (as were the posters at the exhibit), but I figured it would be very unlikely for someone to have a Gepard and not speak German, so if you have and do not – read this blog :-).

I will provide all digital material I have via this blog.

I also plan to find a way to have the software available for download. However, this might take a while because the original distribution media are 3.5 ” floppy disks with a proprietary format.

Finally, if you have a Gepard, I would love to hear from you. There are not many of us around. The same holds true if you were one of the developers or original users. Send me an email or write a comment.