Clock rate

NTSC/PAL differences

Consoles in the USA and Europe run at different speeds due to the different television standards used. The main differences between the NTSC and PAL PPUs is as follows:

Property	NTSC	PAL
Master clock speed	21.477272MHz = 236.25 MHz / 11	26.601712MHz
PPU clock speed	21.477272MHz / 4	26.601712MHz / 5
Corresponding CPU clock speed	1/3 PPU clock speed	1/3.2 PPU clock speed
Height of picture	240 scanlines	240 scanlines
Nominal visible picture height (see Overscan)	224 scanlines	268 scanlines
Length of VBLANK	20 scanlines	70 scanlines
Timing quirks	First scanline is one PPU cycle shorter during every other frame	None

Other than these differences (and video output), the NTSC and PAL PPUs function exactly the same.