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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 (!).
![](images/Siemens_PCD-2-frontal.jpg)
Interesting look inside the system:
![](images/Siemens_PCD-2-opened.jpg)
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.
![](images/Siemens_PCD-2-BIOS.jpg)
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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