But if we look at their headers, we can see that the USA version contains the value "J" at address 0x1F0 while the European version contains the expected value "E" at address 0x1F0
So my question is, what is the most relevant indication for identifying the "region" of a ROM? The tag in the file name or the value in the ROM header?
Or in other words, how was the region tag in the ROM files names defined, on what criteria?
The file names are from what would ideally be verified from actual carts as the region source(s) of each ROM.
Do not expect that the ROM headers are always correct. They are in fact not always correct.
I just checked and Two Crude Dudes and Captain America and the Avengers, both ROMs I dumped myself from USA carts contain "J" strings.
Captain America, I believe, was not even actually released in Japan.
Even the header checksums are correct MOST of the time but there are definitely released games that don't have a correct checksum.
Some may even have the wrong ROM size in the header. I know that Zero Wing (both Japan and Europe versions) have the incorrect ROM size in the header, I had to alter the Retrode devs about that long ago.
Heck, the Castle of Illusion cart I dumped (which I believe is Canadian) says "SEGA MEGA DRIVE" in the header and "US" in the header. (from an odd Canadian box variant with "Genesis" box and "Mega Drive" cart, which differs just very slightly from the US boxart. The standard Canadian box at least I recall is distinct from the US. It had at least French, if not reusing the EU mulit-language art.)
So the tag in the file name can therefore be considered as "historical" data to be carefully preserved, as without it, it would be difficult to find the region of origin based on the file's binary data alone.
Good to know, and thanks for the clarification.
This makes no-intro work even more valuable. Well done!
