Clock rate: Difference between revisions
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(added divide values for CPU clock speed) |
(turned timing quirks into total dots per frame; added vertical scan rate and NTSC-specified tolerance for master clock speed) |
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! Property || NTSC || PAL | ! Property || NTSC || PAL | ||
|- | |- | ||
| Master clock speed || 21. | | Master clock speed || 21.477272 MHz ± 40 Hz<br>236.25 MHz / 11 by definition || 26601712 Hz ± ?<br>26601712.5 MHz by definition | ||
|- | |- | ||
| PPU clock speed || 21. | | PPU clock speed || 21.477272 MHz / 4 || 26.601712 MHz / 5 | ||
|- | |- | ||
| Corresponding CPU clock speed || 21.47MHz / 12 = 1.78977267 MHz | | Corresponding CPU clock speed || 21.47MHz / 12 = 1.78977267 MHz<br>3 dots per CPU cycle || 26.601712 MHz /16 = 1.662607 MHz<br>3 1/5 dots per CPU cycle | ||
|- | |- | ||
| Height of picture || 240 scanlines || 240 scanlines | | Height of picture || 240 scanlines || 240 scanlines | ||
| Line 15: | Line 15: | ||
| Length of VBLANK || 20 scanlines || 70 scanlines | | Length of VBLANK || 20 scanlines || 70 scanlines | ||
|- | |- | ||
| | | Total number of dots per frame || 341*261 + 340.5 = 89341.5<br>(scanline 261 is one dot shorter in every other frame) || 341*312 = 106392 | ||
|- | |||
| Vertical scan rate || 60.0988 Hz || 50.0070 Hz | |||
|} | |} | ||
Other than these differences | Other than these differences and color encoding, the NTSC and PAL PPUs function exactly the same. | ||
Revision as of 13:55, 28 March 2010
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 | 21.477272 MHz ± 40 Hz 236.25 MHz / 11 by definition |
26601712 Hz ± ? 26601712.5 MHz by definition |
| PPU clock speed | 21.477272 MHz / 4 | 26.601712 MHz / 5 |
| Corresponding CPU clock speed | 21.47MHz / 12 = 1.78977267 MHz 3 dots per CPU cycle |
26.601712 MHz /16 = 1.662607 MHz 3 1/5 dots per CPU cycle |
| Height of picture | 240 scanlines | 240 scanlines |
| Nominal visible picture height (see Overscan) |
224 scanlines | 268 scanlines |
| Length of VBLANK | 20 scanlines | 70 scanlines |
| Total number of dots per frame | 341*261 + 340.5 = 89341.5 (scanline 261 is one dot shorter in every other frame) |
341*312 = 106392 |
| Vertical scan rate | 60.0988 Hz | 50.0070 Hz |
Other than these differences and color encoding, the NTSC and PAL PPUs function exactly the same.
