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For years, I've heard "4%", repeated over and over. But then I read this today:

The original release of the Super Game Boy runs about 2.5% faster than an original Game Boy.

And the source is the people who made the hardware modification fix thing, so they probably know what they are talking about: http://www.qwertymodo.com/hardware-projects/snes/super-game-boy-clock-mod

So why does every other source seem to always say 4%?

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  • 1
    Why does factually-incorrect nonsense get propagated all over the internet? Because copy'n'paste takes less time than thinking. But apart from that, from a pure system-performance point of view, the difference between 1.025 and 1.04 seems like not worth worrying about. May 19 at 0:17
  • 1
    @another-dave "the difference between 1.025 and 1.04"?
    – Rogar E.
    May 19 at 0:19
  • 3
    2.5% faster = 1.025 of base speed. 4% faster= 1.04 of base speed. May 19 at 0:20
  • 8
    @another-dave As much as I share your view on this as being irrelevant, it does make a difference for some extreme use cases, especially speed runs. they depend as much on frame rate as they do on skill. Frame rate is the clock beat of such games, controlling all aspects of movement. Over the course of many minutes a 1-2% faster frame rate does add up to several seconds - eventually more than what lies between equally highly concentrated players.
    – Raffzahn
    May 19 at 1:51
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    @another-dave Of all the places for something not to care about, this is the least relevant. For most intents and purposes, the content on this SE is useless. But that doesn't stop us from being interested in the details of old systems, and wanting to know how things work. May 19 at 1:59
35

For Gameboy clocking 3 'generations' need to be seen

  • All 'classic' Gameboy, that is the original all the way including micro run (the 8 bit CPU) from the same 4.194 MHz MHz crystal, divided by two, for a CPU clock of 2.097 MHz.
  • Gameboy Color and later added a double speed mode, allowing the 8 bit CPU to run at 4.194 MHz
  • Super Gameboy does as well run the same CPU, but clock speed was now derived from the SNES system clock, divided by five.

Dividing the SNES (*1) system clock by five comes quite close to the original clock rate, but not exact. In addition the SNES clock differs between NTSC and PAL units:

  • SNES PAL clocks at 21.28137 MHz, so the Super Gameboy gets feed 4.256 MHz
  • SNES NTSC clocks at 21.47727 MHz, resulting in a 4.295 MHz clock

The resulting frequency is either divided further by two for 'normal' operation, or used direct for fast (GBA) speed.

This translates into a speed up of

  • 4.256/4.194 = 1.0148 or 1.5% for PAL units and
  • 4.295/4.194 = 1.0241 or 2.4% for NTSC units.

All of this is essentially without any change to game play, except for some rather offbeat usages - like doing competitive speed runs, or trying to get fastest ever runs. Here a percent up or down may result in several seconds faster or slower.


Long story short: Nintendo (and next to all users) accepted this little difference in exchange for being able to play their old games :))


*1 - It might be worth to add here, for everyone not so familiar with Gameboy generations and details, that the 'Super Gameboy' isn't a hand held game, like everyone might assume, but a cartridge for the SNES containing most parts of a Gameboy, except I/O. Instead the game output is displayed on the TV connected to the SNES, while input is transferred from the SNES controllers (which also introduces a tiny lag - that's why the next generation got an optional dedicated controller - AFAIK).

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  • I wonder why speed runs aren't measured with these differences in mind, e.g. by frame? It seems pointless to even bother recording speedruns without accounting for hardware differences.
    – Polygnome
    May 19 at 16:09
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    @Polygnome I guess because it's way less effort to simply define the hardware to be used. The same way other kinds sport do define the hardware they use - like size of poles, hurdles or the brooms used for curling :))
    – Raffzahn
    May 19 at 16:13
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I think you've been unlucky in your browsing. All the sources I've ever seen say that the Super Game Boy is 2.4% faster than the Game Boy.

The Game Boy's clock speed is 4.194304 MHz. The Super Game Boy divides the SNES's clock speed of 21.47727 MHz (for the NTSC console) by 5 to get 4.295454 MHz. Dividing the last number by the first gets you 1.02411603928, or 2.4-and-a-tiny-bit percent faster.

Independent experimentation also gets a result of 2.4% faster.

Game Boy clock speed referenced from OverClocked (which also shows the clock speed for the Super Game Boy). SNES clock speed referenced from Wikipedia. I know they aren't primary sources, but I think they're good enough for now.

By the way, as I recall, the Japan-only Super Game Boy 2 runs at the same speed as the original Game Boy.

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