Picking the Right ROM for a Patch — Regions, Revisions and Dump Names

About 4 min read · 2026-08-24

Apply enough translation patches and sooner or later you meet a message like "checksum does not match." The patch is rarely at fault. Almost every time, the original ROM is a different build from the one the author worked against.

This article explains why one game has several ROMs, how to read the tags in a filename, and how to check whether the file you have is the one a given patch targets.

Why one game has several ROMs

Regional releases

Home consoles of that era shipped different builds in different territories, and it was not only the language that changed.

• Display standard — Japan and North America used NTSC, Europe used PAL. A PAL build runs about 17% slower and fills a taller frame. Ports that were not adjusted for it play sluggishly, music included
• Difficulty and content — North American builds were frequently made harder, with fewer lives or continues
• Content edits — religious imagery, blood colour, cigarettes and similar details were removed or altered by territory
• Titles and character names — the same game often shipped under a different name in each region

Revisions

When a problem surfaced after release, it was quietly fixed and re-pressed. Those later builds are revisions, tagged Rev 1 or Rev A. The cartridge looks identical; the data is not.

Dump quality

Differences also crept in while reading data off the cartridge. Files with padding at the start, files read incorrectly, and files somebody edited all circulate side by side.

Reading the filename

The naming conventions in general use today are No-Intro (cartridge games) and Redump (disc games). A file following either one tells you what it is at a glance.

Gaiares (Japan).md
Thunder Force III (USA).md
Batman (Europe) (Rev 1).md
Castle of Illusion Starring Mickey Mouse (Japan, Korea).md

Older files often use the earlier style, like Gaiares (J) [!].bin. When conventions are mixed, do not trust the name; verify directly using the method below.

Start with what the distributor wrote down

Whoever made the patch worked against one specific ROM, so the release notes normally say which one:

• Region (Japanese or North American)
• Revision
• File size
• A checksum such as CRC32 or MD5

Of these, the checksum settles it. Whatever the file is called, an identical checksum means an identical file.

Confirming your ROM

Drop the original and the patch into the file inspector separately. Nothing is uploaded; it is all read inside your browser.

What the patch tells you

What the original tells you — file size and internal structure. For a disc game the disc ID also appears, which pins down the region.

When it still will not work

"Checksum does not match" The most common case by far: a different region or revision. Re-read the target version the distributor listed.

It patched, but the text is garbled The ROM was right and the runtime is not. Set your emulator's region to match the original, and try a second emulator.

The file size differs from what the distributor listed You may have a dump with padding at the front. Mega Drive ROMs use .md, .gen and .bin interchangeably and the contents are usually identical — but builds carrying a 512-byte header do exist, and those come out the wrong size.

There are several patches Some games get a separate patch per regional build. Take the one matching the ROM you have.

Summary

• Region, revision and dump quality all produce different files for the same game
• Read the (Japan) and (Rev 1) style tags first
• A checksum beats a filename every time
• When in doubt, open the patch and the original in the file inspector

The application procedure itself is covered in How to Apply a Translation Patch. Available patches are listed by console on the translation patches page.