Clock rate: Difference between revisions

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Revision as of 07:15, 11 June 2009

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.