NEC PC-100 is a personal computer based on 8086 (more pictures are here). Submodel PC-10030 is equipped with a color framebuffer board. Even with the color framebuffer board, CRT still connects to the connector on the motherboard. PC-10030 is usually used with a proprietary display PC-KD651, which supports pivoting (changing display orientation). This information is preliminary as we only figured out the protocols of video signals so far (we assume pivoting is just a switch though).
D-sub DE-9M connector on the motherboard:
------------- \ 1 2 3 4 5 / \ 6 7 8 9 / \_______/
Signal levels are VGA compatible, but the synchronization frequency is out of range of VGA signalling. Some displays support this freqency however.
Currently my PC-100 is working but the MS-DOS system disk is broken. If anybody can privide me with those diskettes, please send me an email.