Hardware Original GBA with AGS-101 Screen - Overclocking Problems!

[ThisisMrBurns]

Hellooo, I've recently carried out a mod where I've put the brighter backlit screen from the newer GBA SP into the nicer to hold Gameboy Advance. It works great, with a brightness switch as well. I then went on to put in the option to overclock with an 8mhz CO, with a switch also, for those boring moments in the game where you're grinding out the xp! The problem with this is that when I overclock, it doubles in speed as predicted, but the screen also increases in brightness/contrast to the point where you can no longer see most colours. I tried with a 6mhz crystal thinking the 8 was too high (and remembering that the backlit screen refresh rate wasn't too good, if that has anything to do with it) but the same thing happens again - same brightness/contrast and all, so its not a matter of what speed you're playing... just the increase in speed itself? If anyone could help me that would be great, I'm not an expert in modding so this is more of a head scratcher than usual! What is going on here?

Thanks

 

[rs1n]

It sounds to me that more than the CPU depends on the crystal for proper frequencies. The screen itself must refresh at a proper rate, and my guess is that it too depends on the correct frequency (likely of the same crystal). It sounds to me that you are overdriving the screen, and I would wager you are getting ghosting effects.

 

[ThisisMrBurns]

That's what I thought. There must be a way to keep the brightness/contrast the same while upping the speed of gameplay? Change how the screen connects through the pins maybe? I'd have no idea how to do that though haha, I don't know what each pin is responsible for. Seperate crystal for the screen? How I'd incorporate that into the circuit I don't know either, if it's even possible... There's no ghosting at all, it's simply the brightness/contrast that is affected only. For example, if I put the screen to an angle I can just about make out the few outlines. When it plays the intro to monsters inc., there are flashes at the beginning of each scene where the colours are just right, then it goes white. Don't know if that's helped describe things a little better... It's annoying because I've seen overclocked gameboys, advances, advance sp's running off 20mhz crystals fine, yet I can't put an 8mhz in mine without it looking terrible. I'm really hoping the two mods are compatible with each other. Any solution around this problem would be appreciated.

 

[ThisisMrBurns]

Right, I've found out that one of the pins is the DCK, which is the Data Sampling Clock Signal, or Dot Clock. So I'm guessing that it is responsible for the frequency at which the screen refreshes at or something along those lines... Could anyone suggest how I would run that at the original frequency of 4mhz while the CPU runs at any other speed? Can you even use two different crystals to run at different speeds in the same system without the higher one cancelling the other out?

 

[ThisisMrBurns]

I realise I'm just replying to myself here haha, but for those who are still looking this thread up because you're going through the same problem or just curious, I figured out a solution, with the help of Robin Farrell (his Youtube channel).

The AGS-101 screen has it's own clocking system in order to keep the refresh rate within it's capacity.... that's about all I know ha. But long story short, when overclocking the CPU, you must ground the Vcom pin in order to keep the brightness/contrast at it's original state. As long as this pin has a wire soldered to the GND pin, it'll work fine, regardless of what speed you switch to. This is a little summer project of mine and I will be doing this to several GBA's, with custom paintjobs and will be up for sale at some point too. Will put a video up of it soon...

 

[Darkipod]

Holy shit, this seems awesome, you best get a tutorial out, you do have a switch hooked up for this, yes?

 

[ThisisMrBurns]

I'll get one up at some point. Yeah there's a switch, it works pretty well. I need to test it out some more...

 

[Darkipod]

God I want to do this for my GBA Build.

 

[Nusdogg]

How hard is this?

 

[Darkipod]

Sorry to bump this but have you gotten around to a overview of the mods?

 

[ThisisMrBurns]

Haha sorry mate, I never got round to doing a tutorial! I have to admit, I did a school boy error, messed up my soldering iron (and 3 circuit boards in the process) and never got back to carrying on with the project. I did however get one finished ha! It works a treat. I've put a little demonstration of it up on Youtube. The rest of the GBAs I have are ready, they literally just need soldering and put back together. I might finish it off at some point in the future...

 

[Shadow#1]

I'm looking for info on the brightness switch were to find?

 

[Darkipod]

Damn man well could you upload some pics!? I just need to see how you are overclocking and how you fixed the screen issue.

 

[Darkipod]

Haha sorry mate, I never got round to doing a tutorial! I have to admit, I did a school boy error, messed up my soldering iron (and 3 circuit boards in the process) and never got back to carrying on with the project. I did however get one finished ha! It works a treat. I've put a little demonstration of it up on Youtube. The rest of the GBAs I have are ready, they literally just need soldering and put back together. I might finish it off at some point in the future...

Hey man im trying to find your youtube vid, however searching for gba overclocked gave me some info on something called the GBAacellerator.