CRC-32

[Jason Siebert]

I have a file that seems to be wrongly calculated for the CRC, [BIOS] Hang On (USA, Europe) (v3.4).sms

In the picture you can see the file I have is calculated at 161fbfcf in Romcenter and the correct CRC is 8edf7ac6 for the missing file. I ran the file through 2 programs and they both calculated the CRC to be 8edf7ac6. There is an earlier reported bug with the same file having the same issue.

I have found 17 other files with the same issue under Super Nintendo.

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[Eric Bole-Feysot]

Hello, your datafile probably uses the sms plugin ('sms' should be displayed in status bar). See plugin [RomCenter wiki]
This plugin works well with sms games, but unfortunatly, bios have a different layout and should be calculated using standart crc plugin. This improvement is to be done.
Until then, you can reload the datafile and when romcenter asks which plugin to use, use the arcade crc plugin.

[Jason Siebert]

How about the 17 games that use the Super NES sfc plugin? Are you aware of that CRC issue too?

[Eric Bole-Feysot]

Can you provide some snes games with wrong crc ? I will have a look.

[Jason Siebert]

Cassette Kensaki - NUS-you S Cassette (Japan) (En)

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[Jason Siebert]

That first one is to show you that I did verify the CRC32 before sending you more. These are some others:

Lion King, The (USA) (Beta 2)

Lobo (USA) (Proto)

Mario Paint (Japan, USA) (Beta)

In total, I have 17 that are like this. Please let me know if the 4 I have informed you of are not enough. I’ll post the other ones if needed.

[Eric Bole-Feysot]

Thanks I will check that rom.

[Eric Bole-Feysot]

So here is the result:

ucon64 rom scan:

G:\ucon64-2.2.2-win\Cassette Kensaki - NUS-you S Cassette (Japan) (En).sfc

Multi Game Doctor 2/MGD2/Multi Game Hunter/MGH

00007fb0 ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ................
00007fc0 ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ................
00007fd0 ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ................

Super Nintendo Entertainment System/SNES/Super Famicom
.....................
Unknown
South Korea
1048576 Bytes (8.0000 Mb)

Padded: No
Interleaved/Swapped: Yes
Backup unit/emulator header: No
HiROM: No
Internal size: 128 Mb
ROM type: (ff) ROM + SRAM + Unknown
ROM speed: 120 ns (FastROM)
SRAM: Yes, 0 kBytes
Version: 1.255
Checksum: Bad, 0x0f4d (calculated) != 0xffff (internal)
Inverse checksum: Bad, 0xf0b2 (calculated) != 0xffff (internal)
Search checksum (CRC32): 0x4e074839
Data checksum (CRC32): 0x2b92dc3c

As you can see at the end, romcenter is calculating the Search checksun, it means romcenter is using the snes plugin.
Romcenter plugin will not simply get the crc, it will analyse the rom, and calculate the crc of the game code, skipping any header added by cartridge copy hardware.
This way, romcenter is able to identify identical games (same search checksun) dumped by different hardware (different data checksum).

To use the plugin, you need a datafile with search checksum crc (no-intro should be like that).
If you don't have such dat, you can deny using plugin when you create a romcenter db.