Re: 6809 in a C64

From: J. Alexander Jacocks <jjacocks_at_gmail.com>
Date: Wed, 23 May 2018 11:31:10 -0400
Message-ID: <CAF-r0Y1UBnWDeQCnpjcdwgkVq2XN70YzeDBZwMK+OeubGMUTZg@mail.gmail.com>
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

Archive generated by hypermail 2.2.0.