Post #3998733

2026-07-21 18:24 UTC

But why did IBM care about black and white composite monitors all of a sudden? Because of the IBM Model 5155, the PC Portable. Inside this computer was a full-length, desktop-compatible CGA card, which attached to the internal amber composite monitor with a header that you can find on your regular CGA card too.

Replies (1)

@gloriouscow@oldbytes.space 2026-07-21 18:26

PC Magazine's review of the 5155 goes into the sort of technical detail that feels bizarre today but was just normal for the 80's when computer users were expected to be technical: The Portable PC is available only with the color graphics card. The display monitor uses the composite output of the card in order to produce a monochrome image instead of the color image. To this end. the card has been modified to produce a better gray scale (or amber scale in this case). The balancing resistors that blend the red. blue, and green color signals into the composite signals are optimized for the portable machine. Blue, which used to disappear on a monochrome representation of the color screen, is now rendered as a fuzzy, reduced-brightness image. https://archive.org/details/PC-Mag-1984-05-29/page/116/mode/2up?q=cga

Open ##3998731