UNIVERSE BIOS crc32 support, input needed

Razoola · Dec 11, 2002

Hi,

I am going to add crc32 checksum support for games P Roms but am not sure of the best way to do this for several reasons.

The main concern I have is the fact that it is not possible to detect the P rom setup in the cart. Because of this my main worry is carts holding the same game but having different P rom ammounts (2x512k or 1x1mb for example).

Keeping this in mind how should I actually do the crc check, some posibilities are;
<ol type="1">[*]Use P rom sizes used in MAME and check actual P rom crc32. The drawback is this won't be accurate for games using a different ammount of P roms than mame and the P rom reported bad could in cases be wrong. Also some games may report a different crc than mame while still being correct because of custom ports in the high ROM bank space (0x2ffff0 and up).
[*]crc32 the actual neogeo ROM and ROM bank space for the ammount the game uses according to mame. This way more allows for a inbuilt table of what crc32 should be for games. The drawback is it won't always be be apparent what P rom holds the error if there is one.
[/list=a]
Anyone have any other ideas how it could be done, personally I feel the second approach is better?

Raz

[ December 11, 2002: Message edited by: Razoola ]

Clear Paper · Dec 12, 2002

Hi Raz,

For 1.
Is it possible to detect the presence of the address comparator to the second set of inputs to the demultiplexor? If so, I imagine it would be possible to detect the presence of the EP roms, which you can then checksum.

I have 4 original Fatal Fury Special carts all in different P arrangement and have dumped and compared the roms. Let me know how I can assist you.

For 2.
Would this function be useful? Wouldn't a bootleg of a good dump come up the same as an encrypted board? (e.g. fully decrypted KOF99 bootleg VS encrypted KOF99 original)

J. Max · Dec 12, 2002

The fact that you can even consider doing this makes you cooler than 99% of the people on this planet...someone really ought to move this to tech support, though.

Razoola · Dec 12, 2002

Originally posted by Clear Paper:
Hi Raz,

For 1.
Is it possible to detect the presence of the address comparator to the second set of inputs to the demultiplexor? If so, I imagine it would be possible to detect the presence of the EP roms, which you can then checksum.

I have 4 original Fatal Fury Special carts all in different P arrangement and have dumped and compared the roms. Let me know how I can assist you.

For 2.
Would this function be useful? Wouldn't a bootleg of a good dump come up the same as an encrypted board? (e.g. fully decrypted KOF99 bootleg VS encrypted KOF99 original)<hr></blockquote>

1) To my knowledge it is not possible to detect the ammount of P roms. There may be a way for the 68k to detect it but I have no idea how unless the cart reports it in some custom port somewhere.

I take it all the FFS carts hold the same data? If so this just confirms the reason not to follow MAME P rom ammounts and rather use the entire address space the game uses. Doing it this way all 4 carts would give the same crc as long as the data is the same.

2) The fact that no neogeo games have an internal selfcheck to make sure data hasent gone bad in the eeprom is enough in itsself to add this option (remember it will be P roms only though). Many people could have carts with bad data on and not even realise it.

The crc option would not really there to detect bootleg carts but your right in saying that carts that dont use the banking protection method will give a different crc to the ones that do.

Raz

Clear Paper · Dec 12, 2002

I recall some jumpers connecting to the edge pins when EP roms are present. My gear is not with me now or I could check it out. Soon though.

All FFS enabled P data turned out to be the same.

But you're right, it's quite troublesome to check each and every P rom and comparing the final memory would be so much simpler and straigh-forward.

Out of curiosity, why would an encrypted board present an overall different memory than a unencrypted one?

Razoola · Dec 12, 2002

Originally posted by Clear Paper:
Out of curiosity, why would an encrypted board present an overall different memory than a unencrypted one?<hr></blockquote>

Because on a encrypted board the program code is different to beable to access the custom ROM banks. On nonencrypted P roms of the same game the code is based on using the standard banking system so its different.

Raz

[ December 12, 2002: Message edited by: Razoola ]

Fran · Dec 12, 2002

romzzzzzzzzzzzzzz

nice dhalsim avatar

RabbitTroop · Dec 12, 2002

I can't really help, but how does the ST-V do it? Is there something on the cart that has the expected CRC value for each chip? Just wondering,

-Nick

Clear Paper · Dec 12, 2002

Originally posted by Razoola:


Because on a encrypted board the program code is different to beable to access the custom ROM banks. On nonencrypted P roms of the same game the code is based on using the standard banking system so its different.

Raz

[ December 12, 2002: Message edited by: Razoola ]<hr></blockquote>

Would it be possible to generate a P rom with a standard banking system (through a table) from the encrypted rom? Was this done to generate the KOF99 fully decrypted set or did it exist originally?

Hi Fran,

I'm actually kinda glad about the rom bashing by many members going on on this forum, it at least leaves this forum free of excessive rom talk and concentrates on the Neo for the cool hardware that it is. You just can't get addicted to the Neo from roms. And I'm heavily addicted.

[ December 12, 2002: Message edited by: Clear Paper ]

Razoola · Dec 13, 2002

Originally posted by Clear Paper:
Would it be possible to generate a P rom with a standard banking system (through a table) from the encrypted rom? Was this done to generate the KOF99 fully decrypted set or did it exist originally?<hr></blockquote>

Yes that is possible though to my knowledge all games with the execption of garou were released by snk in a non scrambled P rom format also.

Raz

UNIVERSE BIOS crc32 support, input needed

Razoola

Divine Hand of the UniBIOS,

Clear Paper

,

J. Max

judas,

Razoola

Divine Hand of the UniBIOS,

Clear Paper

,

Razoola

Divine Hand of the UniBIOS,

Fran

today forever

RabbitTroop

Mayor of Southtown, ,

Clear Paper

,

Razoola

Divine Hand of the UniBIOS,