Mia Magnusson wrote: > Maybe they used hires mode to be able to freely select foreground and > background colors? > Bingo! I just downloaded Teledata.CRT and remembered that the title screen has double height text which of course requires either a full set of custom characters or working in hires mode. According to a register dump in VICE, $D011 is set to $3B = hires mode and $D018 = $29. The latter register appears to be set all the time, which kind of suggests there are two buffers of hires data so the program can switch between those. Probably that it loads and generates a videotex page in the buffer not currently displayed and switches to that one when it is done. Whether generating a hires screen for every page loaded had been faster with a 6809 in the cartridge to offload the 6510 inside the computer is beyond my knowledge, but I understand that the BTX cartridges might use the 680x chips more due to the (existing?) hardware decoding solution was based on those CPUs than for speed purposes. Best regards Anders CarlssonReceived on 2018-05-23 17:00:41
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