Good haul of old pc stuph

On Wed, 21 Dec 2005 19:02:06 -0600 Jim Leonard <trixter at oldskool.org> wrote: What sort of signal? Surely not composite video. EGA resolution isn't composite video. I was talking specifically about the IBM EGA card, not all the clone stuff. It's been years since I looked, but I think it's not explained anywhere common. ----- ----- There. I dug into a dusty bookshelf and answered it for myself, and will share: I have the IBM Technical Reference Manual set for the IBM 5531 Industrial Computer. This machine was a rack-mount case system that used all the 'stock' PC-XT cards and peripherals, and the techref has docs for the XT generation product line, including schematics for ALL the later adapter cards, i.e. MDA, CGA, EGA video, the hard and floppy adapters, BiSync, SDLC, Data Acquisition, GBIB card, etc. The EGA Card section even has the ASM source code for the BIOS extension on the EGA card. Looking at the schematic for the EGA card, it appears the two 'RCA' connectors on the backconnector are only connected to pins 4 and 5 of J4, labeled the 'Feature Connector.' This 'feature connector' brings out all of the relevant video connectons from the board to some unspecified additional board. The two RCA jacks are labeled 'J2 Ext Video' and 'J1 Video Jack.' However, according to the schematic, they're just wires going to pins on J4, so whatever external circuitry the 'feature connector' goes to does whatever mix is necessary. There is a text section that describes in detail what each signal on the 'Feature Connector' is but no mention of what would plug into it. This is interesting. Does anybody know more about the Feature Connector and it's uses? Tony? --- (The Industrial Computer Technical Reference even has schematic diagrams for five different IBM floppy drives and the 10MB and 20MB hard drives. And for the Monochrome, PC Portable, CGA and EGA monitors. Alas, no schematic for the Power Supply.)