What was the name of the PlayStation Portable's main processor family?

The PlayStation Portable used a MIPS R4000-based processor family.

Sony designed the PSP around a custom MIPS R4000 CPU, commonly described as a MIPS32-based processor. The chip was produced for Sony by Toshiba and operated at a variable clock speed, with later system software allowing higher speeds than the original launch setting.

The processor helped the handheld deliver 3D graphics and multimedia functions in a compact device. The PSP used Universal Media Discs for games and could also access downloadable content through Memory Stick storage.

The MIPS R4000 answer identifies the processor architecture family, not the graphics chip or the handheld’s overall system-on-chip branding. ARM Cortex-A9 belongs to the PlayStation Vita, while the Cell Broadband Engine belongs to the PlayStation 3.