Re: Some new 8032 Editor/Char roms

On Saturday 25 April 2015, 10:20:48 Marko Mäkelä <msmakela@gmail.com> wrote:
> On Fri, Apr 24, 2015 at 10:50:12PM +0200, groepaz@gmx.net wrote:
> >well, yes, that is correct - however, that only means the TOD clock of
> >the CIA (if any) needs different initialization.
> 
> There is no MOS 6526 CIA in the PET. IIRC, the PETs use two MOS 6522
> VIAs (like the VIC-20) and one MOS 6520 PIA.

ok, i thought the later models (8032 etc) have one.... without CIA it matters 
even less :)
> 
> Even in the Commodore 64, as far as I remember, the 50/60Hz TOD flags in
> the two MOS 6526 are not initialized differently. 

correct - nor does it initialize the TOD at all - or use it in any way :)

> The first C64 KERNAL
> version did not even bother to check for PAL/NTSC. Later ones do, IIRC
> by waiting the raster counter register at $d011/$d012 to wrap around or
> reach a particular line. The result of this check is written to some
> location in the $2xx page, but IIRC it does not affect the operation of
> the KERNAL.

almost - rs232 timing table is selected by using this flag (not that the check 
itself or even the rs232 routines are reliable, but thats another topic =P)

> On the PET, I would expect the 6545/6845 CRTC registers to have to be
> initialized differently for 50Hz and 60Hz timings. I never played with
> the CRTC registers on the PET, so I do not have first-hand experience.
> But, if the processor and peripherals cannot detect if the hardware is
> on 50Hz or 60Hz, it would seem to me that the timings should be
> hard-wired in the editor ROMs, just like in the later Commodore 264
> series where the TED chip can output PAL or NTSC, depending on the
> register settings (and the color clock crystal frequency).

yes and yes - however, the conclusion isnt that "ntsc rom is needed for u.s. 
machine" but the other way around - what makes the machine a "u.s. machine" is 
the editor rom.

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