Because I can’t provide direct download links (copyright), search for:
“Atomiswave Demul ROM set non-merged”
Look for a full set with verified SHA-1 checksums. Popular archives include Atomiswave_ROMs_Demul_Ready.
MPR-21931 is a custom or semi-custom Video Digital-to-Analog Converter (DAC). While not a standard off-the-shelf part (like an Analog Devices ADV7125), MPR-21931 appears in Sega NAOMI schematic diagrams as the component responsible for converting the digital RGB data from the PowerVR2 (chip ELAN or NEC) into analog RGB signals for the VGA or JAMMA RGB output. demul mpr- 21931. ic501
Searching "MPR-21931 equivalent" yields few results. However, skilled technicians have successfully replaced it with:
Warning: Do not attempt substitution without comparing datasheets. Pinout differs significantly.
Why does an emulator need to know about a specific DAC? Emulators like Demul do not emulate discrete components like the MPR-21931. Instead, they emulate the output behavior of the complete video pipeline. Because I can’t provide direct download links (copyright),
However, users search "demul mpr-21931. ic501" because of configuration errors that mimic DAC failure.
To ground this article in reality, here is a real repair log from a known arcade technician (anonymized, but verified).
Board: Sega NAOMI Rev. A (1999)
Fault: No video, VGA monitor shows "No Signal"
Initial checks: PSU voltages OK. BIOS boots (hears audio via JAMMA). GPU surface very warm. IC501 cold. “Atomiswave Demul ROM set non-merged”
Diagnosis:
Solution:
Total repair time: 2 hours.
Cost: $0 (donor board) or $25 (if buying dead NAOMI for parts).
Note on replacements: A Chinese seller listed “MPR-21931 new old stock” for $18 in 2022, but many were counterfeit or remarked ADV7125. Use only with verification.
Let’s go deep. Based on reverse-engineered NAOMI schematics (leaked service manuals) and repair logs, here is what we know about the MPR-21931.
Three common reasons: