Overclocking your GBA

Trying to get homebrew running on your PSP? Want to add a screen light to your Game Boy? Trying to figure out how to work your GP2X? By popular demand, discuss it in here! (This forum is for pre-built handhelds, NOT custom made portables!)

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Arrow-->
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Post by Arrow--> » Tue Nov 18, 2008 3:03 pm

it screwd up my gba even when it was taken out
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Post by themadhacker » Tue Nov 18, 2008 3:04 pm

Arrow--> wrote:it screwd up my gba even when it was taken out
hmm. maybe I didn't get all the solder your dad dropped on the cpu off.
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Post by Arrow--> » Tue Nov 18, 2008 3:07 pm

if theres any left its invisble
i'll try an 8 next time
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Post by Master Kirby » Tue Nov 18, 2008 4:12 pm

eurddrue wrote:does it matter if the contacts are touching for the ocillator either?
Make sure the oscillator is wired in series with the switch. Also, if the leads touch each other it will bypass the crystal entirely. Then the GBA probably would not even have a clock signal anymore.

The GBA SP should work the same as the original GBA.

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Post by tysonDS » Tue Nov 25, 2008 2:31 am

Hi Master Kirby,

Thank you for your well detailed instructions, after reading your instructions it only took 2 minutes to open and install the 8mhz crystal.

I didn't put a switch and just wired the oscillator crystal directly to the old one (as I have 2 GBA's, this is my pokemon levelling one).

Anyway, I just wanted to let you know (seeing as you didn't say up in your post) - Adding an 8mhz does not double the speed it triples it.

When you hook the 8mhz up to the 4mhz it becomes 12mhz. This means the game is running at 300% speed.

I think I will get a 4hz crystal and permanently hook that up.
Because the technology is old, old gameboy games seem laggy compared to todays standard. But if I leave it on 200% it's actually just right for playing.

Thanks again

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Post by Master Kirby » Tue Nov 25, 2008 11:29 am

tysonDS wrote:Anyway, I just wanted to let you know (seeing as you didn't say up in your post) - Adding an 8mhz does not double the speed it triples it.

When you hook the 8mhz up to the 4mhz it becomes 12mhz. This means the game is running at 300% speed.
Are you saying that by placing two crystals in parallel, they act as a single crystal with a resonant frequency equal to the sum of the two crystals? I'm not saying this to argue, but something about that doesn't sound right.

Do you have any sources that explain how oscillator crystals behave in parallel with each other? While I have not been able to find any place that clearly describes this, everywhere that I have read about this kind of overclocking, it has described that the circuit runs according to the largest of the individual crystal's frequencies.

If I am wrong, I would be glad to see some information that would explain how crystal oscillators actually work in parallel. It just doesn't look like my GBA was running at 300% normal speed when I have it overclocked with an 8Mhz crystal. If you go to the Japanese website where they overclocked the DS, they also refer to the overclocked speeds as 1.4x and 1.7x for using the 24 Mhz and 28 Mhz crystals.

I guess if someone timed an in-game event while in normal speed, and compared it with the time to do the same event in overclocked mode, that would tell what the real speed was.

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Post by tysonDS » Tue Nov 25, 2008 5:02 pm

Hi Master Kirby,

I'll try to confirm this tonight, I could be wrong though!

What I will do is hard wire a 4hz crystal osc to the default 4hz crystal osc - if the game runs faster than normal this would indicate the crystal osc's are stacking.

If it doesn't stack then this further confirms that I am a dumb ass. :lol:


Either way... still a very cool mod, levelling in pokemon crystal is so much easier now. :D

Thanks again

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Post by nitro2k01 » Tue Nov 25, 2008 9:36 pm

The speeds should not add up like that, but on the other hand placing to crystal in parallell is like enterring a twilight zone. A crystal "wants" to oscillate with it's own frequency, so it's possible that they're interfering some strange way. That could expecially be true as it seems like the GBA is boosting the clock frequency with a PLL. If the input clock signal is notclean it might have unexpected effects.
(The crystal is 4 MiHz while the CPU is running at 16 MiHz in GBA mdoe, meaning that there must be a PLL to up the frequency.)
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Post by gamefreakfatty » Thu Dec 11, 2008 9:11 pm

Great guide, very detailed. I couldn't find any crystal oscillators to take off of other electronics at first. Eventually I realized that I had a dead PS1 screen. I took the oscillator off that. It works!

On another note:
I'm not sure how old the posts are (and I don't feel like checking) that say they only get a white screen when they turn their GBA on, but I noticed that if the oscillator was bypassed (the two wires were connected directly somehow) then it would slow down a lot. I thought that I killed my GBA, but it turned out that the metal case on my oscillator was touching both wires, resulting in the white screen. I undid the wires on the (PS1 screen) oscillator and it returned to normal. Actually, I started playing a game and connected the two wires just to see what would happen. The game went really slow. It took 10+ (I think) seconds before the "GAMEBOY" text appeared when I turned it on with the wires shorted.
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Post by Kyo » Fri Dec 12, 2008 5:06 am

gamefreakfatty wrote:Great guide, very detailed. I couldn't find any crystal oscillators to take off of other electronics at first. Eventually I realized that I had a dead PS1 screen. I took the oscillator off that. It works!
Every game console and TV related device should have a crystal, generally.

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Re: Overclocking your GBA

Post by glassjoe92 » Thu Jun 04, 2009 7:38 pm

Could you rather use a scroll wheel or something similar, a lot like the one used for volume, to turn the processing speed up or down. Instead of directly on or off?

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Re: Overclocking your GBA

Post by eurddrue » Thu Jun 04, 2009 8:52 pm

glassjoe92 wrote:Could you rather use a scroll wheel or something similar, a lot like the one used for volume, to turn the processing speed up or down. Instead of directly on or off?
The gba probably wouldn't register the change in frequensies and you would be left with the same speed you started out with. However, there is a kit you can buy that lets you change from normal, to 1.5x, to double the speed by using the shoulder buttons and the select button I believe. I'm pretty sure palmertech used it in his GBOMG clone.
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Re: Overclocking your GBA

Post by palmertech » Fri Jun 05, 2009 10:14 pm

It has a slow mo mode, too. I have one, it is nice.

A REAL variable oscillator with a dial would be so much win, though.
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Re: Overclocking your GBA

Post by mog123 » Sun Jun 28, 2009 6:42 pm

palmertech, there is something called RC oscillator, By using a potentiometer and trimmer instead of a resistor and capacitor, that might work, though I'm not sure.

Anyway, has anyone tried going over 8? To something like 10-12?

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Re: Overclocking your GBA

Post by HotDog-Cart » Sun Aug 02, 2009 10:42 pm

Over 9000 anyone?
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