On Saturday 25 April 2015, 10:20:48 Marko Mäkelä <firstname.lastname@example.org> wrote: > On Fri, Apr 24, 2015 at 10:50:12PM +0200, email@example.com 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. -- http://www.hitmen-console.org http://magicdisk.untergrund.net http://www.pokefinder.org http://ar.pokefinder.org Programming today is a race between software engineers striving to build bigger and better idiot-proof programs, and the Universe trying to produce bigger and better idiots. So far, the Universe is winning. Message was sent through the cbm-hackers mailing listReceived on 2015-04-25 13:00:07
Archive generated by hypermail 2.2.0.