Re:Hoard-of-bitfonts: bitmap fonts from disused operating sy...
by megameter on Thursday July 08, 2021 @03:32PM
(#27776636)
The term "character generator" in video specifically refers to hardware that overlays text onto the video signal. That is, in this case it's not a "text mode", it's a bitmap graphics mode used for text, which appears likely just going by the screenshots. There weren't many computer systems taking this approach in 1978, since any bitmap mode would be RAM-hungry, so they were usually either text centric(Commodore PET) or had both text and graphics modes and hybrids(Apple II, Atari).
Re:Hoard-of-bitfonts: bitmap fonts from disused operating sy...
by LocalH on Thursday July 08, 2021 @02:09PM
(#27775743)
It probably means the hardware had no dedicated text mode with a separate character ROM, but that the software would draw the bitmaps to the graphics screen itself.
Re:Hoard-of-bitfonts: bitmap fonts from disused operating sy...
by phkahler on Thursday July 08, 2021 @08:23PM
(#27779227)
We disassembled the 2k rom back then. There are routines for drawing text, character by character, pixel by pixel. The code is terribly not-optimized but fits in 2k including the character set. Hardware just has a single frame buffer at a fixed address. 4 pixels per byte, 32 bytes per line, and that includes over scan and horizontal blanking so 112 to 114 pixels wide 3 scan lines tall. Doubling the pixel clock, devoting more ram to it, and using the empty rom socket would have made it quite a machine for back then.
Of course, those are lying. https://www.old-computers.com/museum/computer.asp?st=1&c=100... says “The Interact shipped with 2 joysticks, a built-in tape recorder, a TV RF modulator and 2 KB of ROM”.
So, in real life, those characters were filtered through a NTSC tv signal.
Also, the last comment on https://www.old-computers.com/museum/doc.asp?c=1004 claims “It had no character generator, formin it's large letters from graphic routines.” That seems to imply all characters were drawn procedurally, not from a bitmap font. I find that unlikely. Can that be done in less memory than a generic blitter would use?
There even is a link to emulators on https://www.old-computers.com/museum/emulator.asp?c=1004&st=.... One of them led me to http://dchector.free.fr/link.html, which has a few emulators for (AFAIK) obscure systems such as “Thomson MO5NR, Thomson MO6 & Olivetti Prodest PC128” and http://dchector.free.fr/download/interact_rom.zip, which, presumably, is the ROM for this system.