Demul is a discontinued but still widely used emulator for Sega’s arcade hardware: NAOMI, NAOMI 2, Atomiswave, and Dreamcast. It became famous for its relatively accurate HLE (High Level Emulation) of the PowerVR2 GPU and the custom audio DSP.
When someone searches for "demul mpr-21931. ic501", they are likely encountering a graphical glitch, missing sprites, or a black screen in Demul and are trying to map the emulated hardware error back to a real-world component.
For most users, the practical answer is: run NAOMI games on a PC using Flycast with a CRT shader, and store your real NAOMI board as a collector’s item. The MPR-21931 is not being manufactured again. demul mpr- 21931. ic501
This string is not random gibberish. It follows standard Sega arcade hardware naming:
In short: Demul is looking for a specific ROM file that it cannot find in your game’s zip folder. Demul is a discontinued but still widely used
This almost always happens with Atomiswave games, particularly titles like Dolphin Blue, The King of Fighters Neowave, Demolish Fist, or Rumble Fish 2.
Searching "MPR-21931 equivalent" yields few results. However, skilled technicians have successfully replaced it with: This string is not random gibberish
Warning: Do not attempt substitution without comparing datasheets. Pinout differs significantly.