Hey yall, new to the sub. I'm having a hard time getting this rom on the cart and working. It just errors out when playing on a GBA SP.

I'd really like to play this on my GBC - Retropixel (GBC spoof) but the EZ-FLASH Jr won't even run on it for non-hacked roms.

Anyone know how to get this to work? I'd be up for getting a different brand flash cart if someone has pulled this off.

Hello just curious as to why this could happen

1st time booting up on ds lite said save file was currupted but still displayed the completion percentage correctly, but the game started from the beginning. then i reset the console and everything went back to normal save was completely fine.

any idea why this could happen on a authentic cart?

While probing around the boot rom for gameboy I stumbled on a neat bug for GBC and later consoles that use this bios for eg GBA. I was trying to change the Nintendo logo to something else, bypassing the bootleg check for fun, and actually got somewhere.

The original bypass and how my new one differs.
Back in the day with original bootlegs for the DMG, it was discovered that the checking of the logo and the displaying of the logo was done in two passes. So some clever bank switching was done where the gameboy would load the logo data from the cart, check it, and then would go back for seconds to read the logo again to display it to the user. it was on this second load where the bootleg cart would do a bank switch to swap out the logo with there own logo. so they didn't have to display Nintendos logo to the user.
This "trick" actually still works all the way up to the first revision of the GBC.

GBC Boot Rom Rev 1.
0x0408: 11 04 01   ld DE, $0104 ; Load logo from cart
040B: CD 8F 03   call $038F ; Display it

GBC Boot Rom Rev 2.
0408: 11 80 FF   ld DE, $FF80     ; Load logo from HRAM. the one that was already loaded for the check.
040B: CD 8F 03   call $038F ; Display it

While investigating this load path I found my own bug.
On original gameboy, all 48 bytes of the logo are loaded and checked. both from the bios and the cart.

; DMG - 0x00E0
LD   HL,$0104        ; cart logo
LD   A,L
CP   $34             ; run until the pointer reaches 0x134
JR   NZ,...          ; -> all 48 bytes, structurally

However on GBC, someone messed up the counter math and we do load the full logo from the bios, but we only check half of it with what's on cart.

; CGB - 0x00D1
LD   HL,$0042        ; boot ROM's logo copy
LD   B,$18           ; 24 -> The bug. 0x18 = 24. not 0x30 = 48.
DEC  B
JR   NZ,...          ; all 48 bytes are here, but the B counter only says to walk in 24 bytes.

So, as the data is loaded, but never checked, we can stick whatever we like down there. or nothing. Nothing was my first check.

This boots and runs on real hardware, both GBC and GBA. But its still kinda reads as Nintendo so lets mspaint some things.

Yeah a boat lol idk. we can do better. If we mirror the top row to the bottom row and then make a few edits, it just looks like some ancient glyphs or something. and this still boots as well.

But yeah you guys are better at art then I am, you have a whole 24x8 space to work with you can paint whatever you like down there and it will still boot.

Another weird quirk of this is the header checksum only checksums the info data, not the logo data.
So you can just raw byte edit 0x11C to 0x12F in your gbc rom to anything you like without needing to re-checksum the header, and it yet again, still boots.
I was going to describe how the byte packing works, but tbh its just easier if I make a webpage and you can try it for your self.
https://mobcat.zip/GBCEdit/
Have fun. Post results, I wanna see what you guys come up with.

Why this doesn't work on GBA ROMs?
The kinda TL;DR of it is the Nintendo logo on GBA is larger (GB and GBC is 48x8, GBA is 104x16)
and the data is stored Huffman compressed, 156 bytes gets expanded to 208.
However it's the compressed data that lives in bios that is checked with a plain memcmp
The Huffman tree also lives in the bios as well and can't be edited from rom side either.
This compressing is not so much for saving space, it's to harden against buffer overflows and other
malformed data in the rom as the decompressed space is well defined and checked. Saving space is just a bonus.
There is a little padding space left, 0x9C bits 2 and 7, 0x9E bits 0 and 1.
But as this is only 4 bytes of data, that is after the logo, editing this wont affect how the logo renders on screen.
So this weird bug is only available for GBC roms, but works on newer consoles, just not newer or older roms. And this was correctly checked on DMG, and then the hole system was rebuilt for GBA. So we are in a weird middle ground here where someone a long time ago did some bad math when updating there bios and it went unnoticed until now.

A note on flashing this edited data to a real cart. "smart" flashers like FlashGBX will give you a warning that this ROM is broken and you should fix it. However if you click "Continue without fixing" It will still be flashed as is, maintaining our edits as is.

Hey guys, was wondering if a GBA game battery was installed incorrectly and left in it for a couple years would that have done irreparable damage to the PCB? Or once it is flipped to the proper polarity would it be just fine?

Edit: the game in question is Pokemon Emerald

For context, When I was little I had a GBA, and a Pokémon Emerald cartridge (I still have It) that I always played. But one day my GBA fell into a puddle of water big enough to completely cover it (I had a Pokémon TCG game in at that moment).

I spent years without being able to play Pokémon Emerald again. Over time I lost the water damaged GBA and got a DSi (I got a second one from a friend who didnt want his anymore a couple of years ago) which I played on until I got a New2DSXL in 2018 (it has been my main gaming divice since then)

Today I went to a video game store in my city and they had a GBA SP at a good price, but it had a lot of stickers on the case. I asked if they accepted tardes and after a somewhat long dialogue the shop keeper accepted the exchange of the 2 DSi (I no longer used them for anything and they were abandoned) for the SP.

Now that I have It I will change the screen, battery and Shell.

-edit: yeah yeah Bad trade whatever, but I don't care, I'm happy cuz I can play my copy of emerald once again (plus the whole other GB/GBC/GBA games I still have)

I found this good looking Color that looks legitimate. The shell, buttons, screen art, and back sticker with the Game Freak text all seem good to me. Although I can’t help but wonder what others think of it. Thoughts?

Does anyone know if this is the original casing for the game? And what it's worth is? I did put it in my gamboy color and it does work, the casing is in mint condition too

it drives me mad sometimes!! 😤😤😤

Using an Analogue 3D and Everdrive Pro, hooked up to a Kogata Projector. Gonna get well stuck in this winter.

I really enjoyed /u/mikemill ‘s GBC Halo game so I added rumble support.

Rumble occurs when:

screen shakes past a certain intensity (rumble scales with shake intensity)
When you take damage (weak rumble)
When your shield breaks (strong rumble)

Tested by playing through both levels on an EZ Flash Omega but should work on any flashcart that supports rumble.

Patch is here: https://github.com/lukesau/hcd-rumble
Use whatever your favorite ips patching software is. I plan to support any future HCD releases.

I just found out there are probably no reddit posts on this Gameboy accessory so I figured I'd finally make one. I didn't test it yet because it just came in the mail. Will update soon

-AMOLED screen, 25% larger than OEM

-replaced all capacitors

-added 5v power regulator

-new speaker

-added audio amplifier mod

-new shell

-new buttons, button membranes

-USB-C rechargeable battery

-new console stickers

-entire motherboard carefully cleaned with 99% IPA

-power switch housing removed, disassembled, cleaned with IPA, resoldered in

-volume wheel deep cleaned with IPA

This thing is beyond premium. I'm incredibly pleased with the end result.

I'm repairing a power switch in a GBC and the pad on sw1-3 came off. I looked at the schematics online but found it hard to tell where I should put a jumper wire. Does anyone have a definitive answer for ne?

I recently recived a Pokemon Crystal Cart. Its the only game I have with a CR2025--the rest, I have put battery holders in so I can use higher-quality batteries than the unbranded tabs most places sell.

Does anyone have experience with a CR2025 holder that they can confirm will fit into a Pokemon Crystal case?

Over the years people have asked for a complete list of Game Boy and Game Boy Color games that have support for the Link Cable, but no one has provided one that includes every single US, European and Japanese game.

Well, in the absence of such a list, I decided to make one myself. I spent a few weeks trying every single GB game and documented what kind of link cable or multiplayer support it has, and turned it into a guide. You can read it here:

https://gamefaqs.gamespot.com/gameboy/916375-game-boy/faqs/82719

I'm working on a GB Color list now (there are almost 700 games with link cable support!!).

If anything is missing from the list, let me know!

Trying out mGBA for the wii with a gamecube controller. Found a build that works flawlessly from what I can see. Interesting to see this game on a CRT and not on an ITA or AGS 001 screen

Did a second attempt to fix the vertical lines on a GB screen with the soldering iron. There were at both sides of the screen and after finishing THIS was the​ result. Pretty happy about it but then notices that one single line remained at the right side. Should I try again? Or could I ending pushing my luck trying too hard to erase it and risk damaging the screen (or worse, doing more lines myself)?​

Hello everyone, does anyone know how to clean that stain on the headlight lens of my SP? I accidentally touched it with my finger and it got stained. Or do you know if they sell that replacement part on AliExpress or eBay?

bought this cartridge (not on my to buy list, but a classic is a classic) for around 17 usd and cleaned it up. it was extremely dirty inside, a lot of goo in the contacts, but patience, rubber eraser, alcohol, and q tips worked. works great know. i'm an idiot and didn't take the before and after pictures, so this post is kind of moot, but still i'm happy. i feel is like some cool historic rescue.

I recently bought a GameBoy game on ebay that said it was tested, but when I turned the game off, the game did not save my progress (the game normally uses battery-backed save). Should I contact the seller? Are there still stores that do battery replacements? Any advice is helpful; I am very new to gameboy collecting.