Jim, This looks to be an excellent beginning. I'm very enthusiastic about the options for using the 6809, as I have always been impressed with the overall execution efficiency of that CPU. Is there any interest for the c128 use of this cart? The 80 column RGB modes would be a significant plus for OS9. - Alex On Wed, May 23, 2018 at 10:28 AM, Anders Carlsson <anders.carlsson@sfks.se> wrote: > 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 Carlsson > > > >Received on 2018-05-23 18:00:07
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