Basically the difference between PAL and NTSC consoles is the frame rate, 50 vs 60 Hz. The consequence of that is that PAL and NTSC mostly differ in number of cycles available for the CPU per frame, with NTSC numbers being significantly smaller.

More sublte differences might be number of cycles per scanline, position of visible screen area related to the frame interrupt and different ratio between CPU and video clock frequencies. Example here is the C64, where there are 63 clocks per scanline in PAL and 65 clocks in NTSC. Ratio between CPU and video clocks is different in NTSC NES/famicom (1:3) and PAL NES (5:16).

Now back to the games. Simple games that are happy with NTSC timings might run flawlessly in PAL, for example "super mario bros." on NES, which runs just fine on PAL NES, not to mention slower gameplay due to slower rate of frame interrupts. The opposite might be problematic -- for example, there were more games for PAL C64 than for NTSC one, and there was a game cracking/adaptation scene on C64 in 80ies and 90ies, which basically ported PAL games to NTSC machines. That required many hackings such as revise game timings, optimize algoriths, etc. as to fit execution into the NTSC frame.

Some timing-sophisticated games for NTSC NES, that do ingenious and perfectly timed tricks to the PPU, might be completely unable to run on PAL NES due to different CPU/PPU clock ratios.

Basically the difference between PAL and NTSC consoles is the frame rate, 50 vs 60 Hz. The consequence of that is that PAL and NTSC mostly differ in number of cycles available for the CPU per frame, with NTSC numbers being significantly smaller.

More subtle differences might be number of cycles per scanline, position of visible screen area related to the frame interrupt and different ratio between CPU and video clock frequencies. Example here is the C64, where there are 63 clocks per scanline in PAL and 65 clocks in NTSC. Ratio between CPU and video clocks is different in NTSC NES/Famicom (1:3) and PAL NES (5:16).

Now back to the games. Simple games that are happy with NTSC timings might run flawlessly in PAL, for example "Super Mario Bros." on NES, which runs just fine on PAL NES, not to mention slower gameplay due to slower rate of frame interrupts. The opposite might be problematic – for example, there were more games for PAL C64 than for NTSC one, and there was a game cracking/adaptation scene on C64 in 80ies and 90ies, which basically ported PAL games to NTSC machines. That required many hackings such as revise game timings, optimize algorithms, etc. as to fit execution into the NTSC frame.

Some timing-sophisticated games for NTSC NES, that do ingenious and perfectly timed tricks to the PPU, might be completely unable to run on PAL NES due to different CPU/PPU clock ratios.

Basically the difference between PAL and NTSC consoles is the frame rate, 50 vs 60 Hz. The consequence of that is that PAL and NTSC mostly differ in number of cycles available for the CPU per frame, with NTSC numbers being significantly smaller.

More sublte differences might be number of cycles per scanline, position of visible screen part related to the frame interrupt and different ratio between CPU and video clock frequencies. Example here is the C64, where there are 63 clocks per scanline in PAL and 65 clocks in NTSC. Ratio between CPU and video clocks is different in NTSC NES/famicom (1:3) and PAL NES (5:16).

Now back to the games. Simple games that are happy with NTSC timings might run flawlessly in PAL, for example "super mario bros." on NES, which runs just fine on PAL NES, not to mention slower gameplay due to slower rate of frame interrupts. The opposite might be problematic -- for example, there were more games for PAL C64 than for NTSC one, and there was a game cracking/adaptation scene on C64 in 80ies and 90ies, which basically ported PAL games to NTSC machines. That required many hackings such as revise game timings, optimize algoriths, etc. as to fit execution into the NTSC frame.

Some timing-sophisticated games for NTSC NES, that do ingenious and perfectly timed tricks to the PPU, might be completely unable to run on PAL NES.

Basically the difference between PAL and NTSC consoles is the frame rate, 50 vs 60 Hz. The consequence of that is that PAL and NTSC mostly differ in number of cycles available for the CPU per frame, with NTSC numbers being significantly smaller.

More sublte differences might be number of cycles per scanline, position of visible screen area related to the frame interrupt and different ratio between CPU and video clock frequencies. Example here is the C64, where there are 63 clocks per scanline in PAL and 65 clocks in NTSC. Ratio between CPU and video clocks is different in NTSC NES/famicom (1:3) and PAL NES (5:16).

Now back to the games. Simple games that are happy with NTSC timings might run flawlessly in PAL, for example "super mario bros." on NES, which runs just fine on PAL NES, not to mention slower gameplay due to slower rate of frame interrupts. The opposite might be problematic -- for example, there were more games for PAL C64 than for NTSC one, and there was a game cracking/adaptation scene on C64 in 80ies and 90ies, which basically ported PAL games to NTSC machines. That required many hackings such as revise game timings, optimize algoriths, etc. as to fit execution into the NTSC frame.

Some timing-sophisticated games for NTSC NES, that do ingenious and perfectly timed tricks to the PPU, might be completely unable to run on PAL NES due to different CPU/PPU clock ratios.