Siemens PCD-2


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An interesting and rare PC/AT compatible: Siemens PCD-2.

This was one of the first german IBM PC/AT compatible computer, some parts came from Tandon. It wasn't build like a conventional PC with a monolithic mainboard, instead it had an ISA (16Bit) BUS backplane. A CPU-card with a 80286 12MHz processor, an OMTI hard drive controller, one drive bay for a 1.2MByte HD TEAC FD55GFR floppy drive and a very uncommon combined CGA/Hercules card graphics was used.
The monochrome monitor get its power via the signal connector (!).

Interesting look inside the system:

There is no space for additional interface cards, but in this system there were already 2 serial/parallel interfaces below the video card inserted.

Interestingly, the CPU card already used SIMM (4x 256KB = 1024KB).

Also, the build in BIOS is uncommon, there is also a field to switch between MFM and RLL, this means selecting RLL instead of MFM is just done via software.

In my system, hard drive is running well WITHOUT choosing any hard drive number.
This is a miracle. When booting, BIOS asks you for what partition should be used (if there is at least one present).

Switching between CGA and Hercules mode is done by using a small DOS utiltity named "CRT.EXE". Siemens delivered the system with MS-DOS 3.20.

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