Demul Mpr- 21931. Ic501 [OFFICIAL]

If you find mpr-21931.ic501 elsewhere (e.g., another game’s zip), do not just copy it — each file is game-specific and will fail the CRC check. You need the exact match for your game.

Three root causes explain why searches for "demul mpr-21931. ic501" dominate repair forums:

| Symptom | Probability | Other Causes | |---------|-------------|---------------| | No sync, black screen | High | Dead GPU, bad BIOS | | Vertical colored bars | Very High | DAC internal short | | Image has "snow" or ghosting | Medium | Faulty VREF or missing 5V_A | | One color channel missing (e.g., no red) | High | Dead output amplifier inside IC501 | | Image works but fades after 10 minutes | Medium | Thermal failure – IC501 heating up |

Because I can’t provide direct download links (copyright), search for: demul mpr- 21931. ic501

“Atomiswave Demul ROM set non-merged”

Look for a full set with verified SHA-1 checksums. Popular archives include Atomiswave_ROMs_Demul_Ready.

Given the scarcity of MPR-21931 chips, the repair community has developed alternative solutions. If you find mpr-21931

Note: If you don’t have a donor, consider converting the NAOMI to direct digital HDMI using a DCDIGITAL mod (bypassing IC501 entirely). This is sometimes cheaper than sourcing a rare DAC.

Demul works best with non-merged MAME 0.222+ ROM sets for Atomiswave.
Check inside the game’s .zip file. You should see files like:

If it’s missing, your ROM is incomplete. “Atomiswave Demul ROM set non-merged”