What MAME NO GOOD DUMP and BAD DUMP warnings mean
A NO GOOD DUMP or NEEDS DUMP warning means MAME's definition lacks a verified dump for a required device or region; there is no expected good file for you to repair by renaming. A BAD DUMP or NEEDS REDUMP warning means the known bytes are flagged as unreliable and a better preservation dump is needed. Record the exact short name, file, region, and build, then check the current official definition. Do not search for replacement ROM packs.
Do this in order
- 01
Record the exact MAME or core version, machine short name, warning text, named file, region, and whether the machine is otherwise marked working or imperfect.
- 02
Run the target build's `-listxml`, `-listroms`, or media audit for that short name and save the relevant status line.
- 03
Classify the evidence as absent expected dump, known unreliable dump, ordinary missing file, or incorrect checksum; these are different problems.
- 04
Check the same machine in the current official MAME definition or release notes to see whether the preservation status changed after your build.
- 05
If you own the hardware and can contribute a lawful dump, follow MAMEdev's contribution and preservation channels; otherwise document the limitation.
- 06
Do not substitute an unknown download, suppress the warning in a public compatibility claim, or state that a boot proves the data is accurate.
Decision and diagnostic table
| Status | What it establishes | What it does not establish |
|---|---|---|
| NO GOOD DUMP / NEEDS DUMP | No verified dump is represented for that required item | That a random file or zero-filled placeholder is correct |
| BAD DUMP / NEEDS REDUMP | The represented dump is known or suspected to be unreliable | That every machine function is unusable |
| missing | Your configured paths do not supply an expected item | Why the item is absent or whether you may obtain it |
| incorrect checksum | Bytes do not match this build's expected identity | That renaming or another archive will repair them |
Dump status describes evidence quality
MAME source definitions attach dump-quality flags to specific ROM regions. They document preservation confidence, not just whether an emulator can read a file.
A machine may start with substituted or incomplete data and still carry a warning. Booting is behavioral evidence for one path, not proof that protected code, color data, timing tables, or device firmware is authentic.
The exact build owns the expected status
A derived core may freeze an older MAME definition. Compare its own audit output with current upstream information, but do not drop current files into the old core merely because upstream changed.
Record both revisions. A status improvement in current MAME is a reason to evaluate an update, not a license to mix romsets or conceal the old core's expectations.
Preservation research is not a download instruction
The warning identifies missing evidence for MAME developers and preservation contributors. It does not authorize copying a board's program, distributing a commercial ROM, or requesting protected files.
A responsible compatibility note repeats the exact warning and test boundary. If the title depends on undumped or bad data, state that limitation instead of claiming complete accuracy.
Dump-status metadata does not grant possession or redistribution rights. Only dump hardware you own when applicable law and agreements permit it, and do not publish, request, or link to copyrighted ROM or BIOS data without authorization.