Re: incorrect C64 wikipedia page?

On Sat, Nov 10, 2018 at 03:48:00AM +0100, Mia Magnusson wrote:
>This page states that there were only NTSC C64's made with the Kernal
>that clears color ram to white no matter what cursor color you had:
>https://www.atarimagazines.com/compute/issue50/286_1_Commodore_64_ROM_Generations.php
>
>But that can't be true.

The -01 KERNAL definitely did that. I think that they accidentally 
copied it from the Vic-20 KERNAL, which always clears the screen memory 
with color 1 (white). On the Vic-20, the screen is white with cyan 
frame, and the text is dark blue (color 6). On the C64, the screen is 
dark blue with light blue background, and the text is light blue (color 
14).

>I'm 100% sure that I were disappointed when the Swedish C64's were 
>changed to Swedish characters and Swedish keyboard layout, and the 
>color memory started to be cleared with the cursor color.

That would be matching the -03 KERNAL behaviour. Did the Swedish C64 
KERNAL change anything else than the maps for the keyboard layout? I 
think that the upgrade consisted of keycaps (or stickers for them), and 
KERNAL and character generator, probably on EPROM.

The -02 KERNAL would clear the screen with the current background colour 
(53281) instead of using a constant. The -03 changed that to the current 
text colour (646).

I documented the differences between the Commodore 64 firmware versions 
that were known to me back in 2003:
http://www.zimmers.net/anonftp/pub/cbm/firmware/computers/c64/revisions.txt

>I'm 100% sure that the C64's I've used back in the days were PAL
>machines, as TV's that can handle both NTSC and PAL were super rare in
>the 80's, especially in the early 80's.

Starting with the -02 KERNAL, PAL/NTSC is detected and the timer 
interrupt is programmed accordingly. The -01 KERNAL was apparently for 
NTSC only, and some timing tables were computed for 1 MHz clock 
frequency, instead of the correct frequency of 14318181/14 Hz or 
17734472/18 Hz.

Maybe the original plan was to use dotclock = 8MHz and divide that by 8 
to generate the bus clock frequency. The 6567R56A has 64 cycles per 
line, while the 6567R8 and later have 65. While 1MHz/64 would be the 
correct line frequency for most PAL variants, NTSC-M uses a higher line 
frequency of 15734 Hz (which matches 14318181/14/65).

	Marko