Post by ilg in FROM BELOW - A Real NES Game! comments

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Hash values are based on content alone, the filename does not have any importance. Thus renaming the file has no effect. On the contrary, any difference in content will produce a different hash (collision excluded)

The crc32 values I have after downloading the files are

from_below_2020_09_16_v_1_0_0.nes -> crc32: 8ce49adb from_below_vs_2021_01_13_v_0_10_0.nes -> crc32: d1616b88

After manually patching the header with the one described in the database, for example with

printf ‘\x4e\x45\x53\x1a\02\x01\x0a\x09\x00\x00\x50\x00\x00\x02\x00\x04’ | dd of=from_below_vs_2021_01_13_v_0_10_0.nes bs=1 seek=0 count=16 conv=notrunc

I get the values reported in the database

from_below_2020_09_16_v_1_0_0.nes -> crc32: 86e935b2 from_below_vs_2021_01_13_v_0_10_0.nes -> crc32: f0232955

Matt Hughson (NES Dev)1 year ago

Sorry about that, I think I had my files mixed up and was getting a false positive.

So looking at the header settings in that database, they did more than just set the rom to ines2. They also set 2 additional settings in the header (looking at the NES version, not VS):

NES Database:

4E 45 53 1A 02 01 00 08 00 00 00 00 02 00 00 01

ROM switched to ines 2:

4E 45 53 1A 02 01 00 08 00 00 00 00 00 00 00 00

The "08" means ines2 format. That is all that I would expect to change.

The "02" means "VS PPU Type = RP2C04-0001"

The "01" means "Default input type = Standard Controllers"

I'm not sure why the database has those changes. To me the correct thing to do is update the database to accurately reflect the actual released ROM. To me the actual ROM should be the source of truth. What do you think?

ilg1 year ago

I would have also expected that the hashes would be of the original image, instead of the image with the newer header (https://forum.no-intro.org/viewtopic.php?t=6772).

Which is why I was asking if there where any drawbacks in using the newer format, which seem to be preferred in some environments.

From https://www.nesdev.org/wiki/NES_2.0 I see that the header is backward compatible and provides some new features.

itch.io

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