Gameboy Player PCB

Currently having an interest in the finer points of ARAM, I set out to see what I could see, and found myself yearning to know how a Gameboy Player makes use of the bus. Unfortunately I could find no scans of the internals at all, so I couldn't really even make educated guesses. So I went out and got one (if you can find them...the stores are pretty much giving them away... :thumbsup: ).

I was pretty bummed to see they actually use an ARM core on this board, I was hoping all the magic was done in the "start up disc"...oh well...

Anyways, here are the shots. Head over to this album if you'd like the first shot in highres.

 

Yeah, not too much magic in these startup discs. AFAIK they only serve to setup the GC into a kinda "video pass-through" mode. From what I've read about them, Datel's GB Player clones are on the other end of the spectrum, with the hardware acting as a simple adaptor to get to the ROM data and everything else running in software emulation. Maybe that's more to your liking? (Then again, if it was, you could just look at a GBA emulator's sources instead...)

 

It looks like a pair of funky platform shoes

 

Yours has an extra errata resister soldered to a test point. Any ideas why or what it does?

 

not at the moment...maybe this would be a good time to ask for an AGB core pinout?

 

Sorry to bump this old thread. The Crystal in your picture is a 33WKSS3CT. While the one in my EU Gameboy player is 33WKSS3BT. I can't seem to find either using google or searching on digikey, so I was wondering if anyone knew if there was a difference?

I get a slight "stutter" when there is a smooth horizontal scrolling object or background in my games that I don't see when I'm using my GameBoy Micro. I guess the reason for this is that the GBA runs at a 59.73Hz refresh rate and that the GameCube does a (poor) framerate conversion to 59.94Hz and thereby adds the stuttering. It would be cool if it was possible to overclock the Gameboy Player just a tiny bit to make the games run at a proper close-to-standard refresh rate. But I guess it might not be as simple as just replacing the Crystal?

 

Sounds like it's time for someone to bust out an oscilloscope and see what they're pushing out.

http://kyorune.com/modding/article.php?id=8 - first gen GBA overclock.

If I get the urge I might crack open both GBA Players I have on hand to see what crystals they use. Very possible they just switched parts as availability waxed/waned or that the B and C stand for revisions of the same part.

 

I thought I read somewhere that the GB Player is basically a full GBA stuffed into a little box, using the Gamecube as the display and input method.

 

Yes, but the GBA runs at a strange refresh rate at 59.73Hz according to this site http://www.coranac.com/tonc/text/video.htm. And the GameCube always outputs in 59.94Hz (Well 59.93 says my XRGB-MIni...) so that difference is probably what's causing the stuttering

 

Same goes for SGB. I understand why they did it for the SNES, with power issues for soft emulation, etc, but don't know why they did the whole shebang in the GCN, wouldn't it just make manufacturing costs a hell of a lot more expensive?

 

Probably had spare chips for the GBA laying around and wanted to sell them.

 

It's common to play asynchronous video everywhere.. Basically the GC will duplicate/drop a few frames every few hundred. Depending on the buffering technique this can cause different artifacts, I'm not sure what the stuttering looks like. Does it look like screen tearing?
Does it only happen when scrolling right or left too?

Overclocking probably won't do a thing since even if you overclocked the GBA frame timing up to 59.94 it won't be PRECISELY the same timing as the GC and the GBA framebuffer will still over/underflow in time, and even if it were precise, they would still be out of phase w/o a PLL, and even in phase the software side of things isn't programmed to take advantage of that so it's just pointless. To fix the problem either the GC should slow down its video and/or implement a better algorithm with more precision so that it never over/underflows. Perhaps the GC doesn't have enough memory to implement double/triple buffering so it just dumps GBA pixels to the screen rectangle in the GC framebuffer as it receives them (which would certainly cause tearing).

 

It's not tearing (thank god). It just makes a slight pause every now and then, where it doesn't on my Gameboy Micro

 

I've never noticed any problems/slowdowns with my GB Player, but then again compared to the backlit GBA which suffers from a slower-than-normal-GBA refresh rate and partial blurring... .
Are you sure the GBA has a 59Hz refresh rate? Seems awfully high to me.

 

I've never heard of a major gaming handheld that didn't "nominally" run at 60hz. (processing game logic, generating video, then the number of times the screen attempts to redraw)
Pixel response time has differences from refresh rate. An 8ms, 16ms, or whatever screen is still generally called 60hz.

 

I imagine it's actually cheaper to do it that way because there would be development costs for a GBA emulator, whereas they already have the GBA hardware - it just needs to be repurposed to the GC. Either way, I think it's pretty cool. I always like to play games on their original hardware, but the one exception to that rule is when new hardware contains the all old console's hardware inside of it - because in that case, the experience is basically 99% the same as the original. The SGB and GB player are examples of this. Other examples are the PS2 (PSX backwards-compatibility), the original PS3 (PS2 and PSX backwards-compatibility), and the Wii (GC backwards-compatibility). The Wii and PS2 have the advantage that they output component - well, the GC has component output too, but it'll cost you a small mortgage.

 

That's the info I could find when I searched around. I can't rule out that it's either my GameCube or GB Player causing trouble (both are EU btw). The stuttering happens no matter how I connect it to my TV being that XRGB-Mini, DVDO Edge or Optoma HD3000. All other GameCube games run smooth

 

The GB Player operates by adding extra RAM to the end of ARAM space (it's supported by the aram controller on the gc). This means that the GBA's screen is actually mapped into this space. If they had wanted, there should be no problem to double or triple buffer this into main RAM (except perhaps some lag). The stuttering is probably just because they are not properly configuring the GC's VI to interpolate the GBA's strange refresh rate to something normal TVs can handle. It's probably possible to do, but I'm not entirely sure...

 

Sorry for bumping an old thread, but I've got some appropriate research data to share and this thread seemed appropriate.


I agree you can't exactly match the correct frequency simply by changing the crystal, but if you can get close enough it could increase the period between doubled frames to several minutes, assuming that the software doesn't need any modifications. I recently decided to investigate this possibility.


I discovered that TP29 on the board allows you to read the vertical frequency. I measured 59.73Hz using an oscope which is the expected value. (Technically I measured 59.72 - 59.74, average 59.73.)


Next I attempted a proof of concept by replacing "Y1" with some crystals having commonly available frequencies to see if the vertical rate could be manipulated. This failed.


I tried several crystals in the 4MHz range and they all yielded a vertical frequency of around 28.8Hz although the value fluctuated (28.6 - 28.9 although some imprecision can probably be blamed on the oscope settings-I'm not very experienced with them.)


Next I tried some crytals in the 8MHz range and here's where it gets strange. The vertical frequency did not change! It was still around the 28Hz range!


Then I tried putting crystals in parallel with the original, like the author of the GBA overclocking tutorial did, even though that was a completely different device. This had no effect on the vertical rate which remained at 59.73Hz.


With nothing connected you get nothing so there doesn't seem to be some other unexpected source generating the 28Hz.


Some loose ends: I don't actually know if the game runs at half speed this way as I never had video connected during this experiment. I was only measuring TP29. Also be aware that you need the boot disc and a game cart installed in order to get the GBP to start running where you can measure things.




Summary- Changing Y1 for crystals of 4-8MHz yielded 28.8Hz vertical frequency on the GBP. This is bizarre as the original crystal is expected to be 4.19MHz and it gives 59.73Hz.


At this point I'm stumped. Can anyone explain this behavior? Any other ideas to try?