The Siemens PC-D is another examples of the machines created in the transitional period of the mid 80s, when the final verdict on the future PC architecture had not yet been passed, and several manufacturers entered the market with their own interpretation of what a PC should look like.
The PC-D differs in some ways from IBM's machines and their clones, and so only specially modified software can be run. Siemens ensured that a lot of important software of the day could be executed - there were ports of MS-DOS, MS Word, MS Windows and some applications, DR GEM, Turbo Pascal and others.
The PC-D was also sold as a Unix workstation running Siemens' Sinix under the PC-X moniker.
Most of this stuff is already posted in the "Requirements" thread, but I've since redumped the BIOS and HD controller ROMS, and it's sorted and cross-linked.
The main differences between the PCD and regular PC clones are:
- 80186 CPU
- proprietary bus with horizontally stacked cards
- non-compatible graphics using the SCN2674 video chip that is also used in MAME's MPU4Video driver
- black and white graphics 640x350
- SCSI on board using Siemens' SM912 SCSI chip, the harddisk is then connected via an Omti 5100 SCSI <=> ST506 controller board
- WD 2791 Floppy disk controller (2793 according to Servicehandbuch p.27)
- Two V24/V11 serial interfaces
- RTC MC146818
- 720KB on 5,25" floppy disks (9 sectors, 80 tracks, 2 sides), ability to read 360K floppies. Later developments by Siemens aficionados extended this to 1.2MB HD disk support.
- 256KB, 512KB or 1024KB RAM with ca. 800KB available to user programs due to the non-IBM-architecture.
- (Part of) the BIOS is contained in the MS-DOS, every DOS version has a BIOS version as well.