Re: about the plus4

On 04/19/2012 09:40 PM, Rhialto wrote:
> On Thu 19 Apr 2012 at 19:03:55 +0200, Gerrit Heitsch wrote:
>> A few features were only found on TED and, as far as I know, never
>> used again in any other Commodore video controller:
>
>> - hardware text cursor
>
> I think the CBM-II machines used that aspect of the CRTC.

The 6545 needed quite a bit of support circuitry to produce a picture. 
It was quite flexible (same as the 6845), I still remember the '80to40' 
program which let me play Space invaders and pacman on the 8032, but it 
was also difficult to program.


>> - hardware reverse characters
>
> The PETs used that, but I think that was basically a XOR circuit outside
> of the CRTC. Probably the CBM-II machines did it too.

Yes, but TED allowed you to disable that feature, so you could either 
save space by only defining 128 characters and have the hardware to the 
reverse or do all 256 chars on your own.

TED also allowed you to disable the double clock feature. This resulted 
in a CPU clock of about 890 KHz (and 2 badlines), but made it easier to 
count cycles.

Not counting the lack of sprites, it's not a bad chip.

I did enjoy playing 'Mercenary' on my C16/64K....

  Gerrit


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