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 Post subject: scrambled graphics CNROM
PostPosted: Fri Dec 22, 2006 8:14 am 
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So i tried putting the goonies on a cart...twice. the first time i made it, the screen was all scrambled, but you could still move the guy and kill stuff. so i thought maybe the board was messed up. so i tried it again on another board, new chips and the same result. there is no re wiring the eproms, so i have no clue what to do.


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PostPosted: Fri Dec 22, 2006 8:52 am 
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If you're referring to Goonies (J), that game isn't CNROM - it uses a custom mapper which accepts only writes to $6000-$7FFF and looks at D1 instead of D0. The game would have to be rather extensively hacked in order to work on a stock CNROM board: bank selects would have to be changed from 0/2 to 0/1, register writes would have to be moved to $8000-$FFFF, and register writes would need to accomodate for bus conflicts. A CNROM hack of this game does exist; however, it does not address the issue of bus conflicts.

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PostPosted: Fri Dec 22, 2006 9:57 am 
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Quietust wrote:
If you're referring to Goonies (J), that game isn't CNROM - it uses a custom mapper which accepts only writes to $6000-$7FFF and looks at D1 instead of D0. The game would have to be rather extensively hacked in order to work on a stock CNROM board: bank selects would have to be changed from 0/2 to 0/1, register writes would have to be moved to $8000-$FFFF, and register writes would need to accomodate for bus conflicts. A CNROM hack of this game does exist; however, it does not address the issue of bus conflicts.


ahh, that makes sense. thanks for the info, i was getting a headache wondering what i did wrong.


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 Post subject:
PostPosted: Fri Dec 22, 2006 10:12 am 
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Quote:
A CNROM hack of this game does exist; however, it does not address the issue of bus conflicts.

It does actually. The version of The Goonies (J) [hM03] I have does prevent bus conflicts.

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 Post subject:
PostPosted: Fri Dec 22, 2006 11:30 am 
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ok, so do i have the one with the bus conflicts:

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 Post subject:
PostPosted: Fri Dec 22, 2006 11:46 am 
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1. It looks like some of the CHR tiles are corrupted.
2. Did you set mirroring correctly?

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 Post subject:
PostPosted: Fri Dec 22, 2006 12:13 pm 
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Quietust wrote:
1. It looks like some of the CHR tiles are corrupted.
2. Did you set mirroring correctly?


all i did was split the .nes file with cajones and then programmed the eproms. im not that knowledgeable on all of the nuts and bolts of rom files. do you set the mirroring when you split the file manually?


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PostPosted: Fri Dec 22, 2006 12:42 pm 
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You must check the mirroring flag on the ROM image and then short the correct solder pad on the cartridge PCB (for iNES "horizontal mirroring", short the 'V' pad; for "vertical mirroring", short the 'H' pad) and unshort the other one.

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 Post subject:
PostPosted: Fri Dec 22, 2006 1:31 pm 
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Bus conflicts will only made your ROM chip and CPU suffer a bit during a few microseconds because they'll try to output different values. This won't damage them, but gets unpredictable bankswitching. However, this DON'T corrupt the tiles (you may just get the wrong tileset), and if you burned the Goonies hacked to use mapper 3 (CNROM), for some reason the hacker DID prevent bus conflicts, so you won't have them normally. The original Goonies have no bus conflicts anyway, since the mapper is located at $6000 so no ROM data is here.
I think you should remove all solder on 'V' pad first (and make sure there is no contact), and then put some solder on 'H' pad to set Goonies the vertical mirroring it is relying on.

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 Post subject:
PostPosted: Fri Dec 22, 2006 1:42 pm 
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it worked!! i desoldered the blob of solder on the "V" and soldered a blob on the "H". thats good to know, cause i have a few games with scrambled graphics ill have to check out. thanks for the help. i cant believe the cyndi lauper song from the movie plays in the background of this game...wierd.


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 Post subject:
PostPosted: Fri Dec 22, 2006 2:04 pm 
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one more question, i have a couple of SLROM games that have the same problem, but they dont have the H or V on the board. how do i check the mirroring?


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 Post subject:
PostPosted: Fri Dec 22, 2006 3:32 pm 
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I think you did have the mirroring wrong *AND* have dirty connector. Clean you carts and you NES connector. If you can, open your NES and narrow the pins so that they grip cards better.

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 Post subject:
PostPosted: Fri Dec 22, 2006 4:11 pm 
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coinheaven wrote:
one more question, i have a couple of SLROM games that have the same problem, but they dont have the H or V on the board. how do i check the mirroring?


The MMC mappers control mirroring through software, so it doesn't matter. Does sound like a dirty connector though (or maybe bad CHR wiring).


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 Post subject:
PostPosted: Fri Dec 22, 2006 7:01 pm 
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coinheaven wrote:
ok, so do i have the one with the bus conflicts:

Image


That looks more like a corrupted data line on your CHR. Maybe you got a floater... that is, a signal that is disconnected and floating, getting a bit of capacitive coupling.

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 Post subject:
PostPosted: Fri Dec 22, 2006 8:08 pm 
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it had to be the mirroring since the title screen didnt come up before i changed it. all i saw was "press start", but after i changed it the whole thing came up like normal. i also had a badminton with half of the screen missing, so i changed the mirroring and it worked fine. i agree with that something is wrong with the chr roms on the SLROMs. what is wrong, i have no idea, because some MMCI games work fine, and others dont. is it better to use SLROM-05 and 06 boards? i seem to have more luck and the eproms fit better.


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