Converting a PAL system to NTSC

[jarreboum]

What are the differences between PAL and NTSC systems? according to some quick research, different TIAs are responsible for the video output and timing. If I were to replace the PAL TIA for an NTSC TIA and rewire accordingly, would it be enough or are there more shenanigans? What does BLK (pin6 NTSC) do?

 

My idea was to have two TIAs piggybacking in a PAL console, wired correctly and with a switch on Vcc so I would be able to choose between PAL and NTSC output. has it been done before?

[Crispy]

I'm not sure if the pixel clock frequency is different between PAL and NTSC systems. If so, then you will have to replace the crystal on your board with with a 3.579545 MHz crystal. I was going to suggest looking at the frequency marked on the crystal, but I just looked at the one on my NTSC board, and it is stamped with a manufacturer part number instead of the crystal frequency.

[AW127]

I dont know if it makes sense to take the risk of modding your PAL-Atari this way, because there exist over 200 PAL60-versions of games, when you look at some threads here. And these games then run exactly like on a NTSC-Atari. Also you can play both versions of games like PHOENIX now on your PAL-console, the normal PAL-version and the PAL60-version, which was made out of the NTSC-version. Sometimes this can be interesting, because not always the PAL-versions are poor, some were already speed-adjusted in the official versions and in this cases, it`s interesting to see the little differences to their NTSC-counterparts, if the NTSC-version was used to build the PAL60-version. And sometimes there are differences in playing.

[jarreboum]

I like modding stuff. I think it's interesting from a technical point of view, to know the technical differences between local variations and if they can be overcame easily. The question isn't really "should I" but "can I".

 

The question has been asked before but never quite answered. These threads have valuable information nonetheless:

http://atariage.com/forums/topic/203273-convert-atari-2600-jr-long-rainbow-pal-to-ntsc/

http://atariage.com/forums/topic/39196-atari-2600-tia-ntsc-and-pal/

http://atariage.com/forums/topic/214203-atari-2600-6-switch-pal-can-i-convert-it-to-ntsc/

 

 

The CSX lines are the Chip Selects. To enable a read or write to the TIA, CS0, CS1 and CS3 need to be low and CS2 needs to be hi. The reason for the different polarities is to make address decoding easier, but it appers that CS2 and CS3 where never used since they are tied to a high and low respectively.

 

The BLK signal indicates that the video is either in the horizontal or vertical blanking period.

 

I am going to gues that PAL-I and PAL-S are the video clock inputs. On the NTCS machine the video frequency is derived from the main system clock, but since PAL uses a different base video frequency a second clock input is provided so that the CPU/system clock can remain the same as the NTCS version.

 

You can get the service manuals from Best Electronics:

 

http://www.best-electronics-ca.com/

 

 

Dan

Your console is NTSC.

PAL boards have a different layout, different TIA and a second crystal needed to generate the PAL signal.

PA120009.JPG

I have yet to take a closer look to the PAL board, but looking at TIA pinouts, I only need to reroute LUM0, LUM2,merge AUD0 and AUD1. I'm assuming BLK is internally merged to COLOR in PAL; in NTSC, BLK is merged to COLOR via a 680ohms resistor, which I sould put back on the PAL system.

[jarreboum]

No one has ever tried this before?