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Tachyon is the codename of the PSP main CPU SoC IC. It is a Sony custom-made LSI which holds the main CPU (Allegrex), the VFPU coprocessor, the Media Engine CPU and its embedded DRAM, the Graphics Engine, the AVC decoder, the Virtual Mobile Engine DSP, the Kirk and Spock crypto engines, and the 4KB embedded mask ROM which holds the iplloader and routines to boot into service mode. Tachyon has one primary CPU core which is responsible for running the XMB and games, and a second CPU core (Media Engine) which implements the audio and video decoding functionality of the PSP.


Main Core "SC"[edit]

The PSP's CPU is a dual core 32-bit Little Endian MIPS based on the R4000 design with a few custom instructions.

Both CPU cores have their own 16 KiB Instruction and 16KiB Data caches. The main CPU has an internal 16 KiB of scratchpad RAM that is accessed directly without going through the system bus.

The main CPU has three coprocessors:

  • COP0 - general system control
  • COP1 - 32-bit Floating Point Unit
  • COP2 - Vector Floating Point Unit (up to 3.2 GFLOPS)

The CPU defaults to 222MHz, but can be configured to run from 1-333 MHz.

The CPU cores are connected to main memory and other peripherals like the Graphics Engine through a system bus that is limited to 1/2 of the CPU's configured clock speed.

Media Engine[edit]

The Media Engine ("ME") is a second MIPS based CPU core that was not directly accessible by licensed developers. Instead, Sony runs code on the ME to facilitate decoding audio and video assets, along with the help of more specialized hardware like the Virtual Mobile Engine and "AVC".

The ME runs at the same clock frequency as the main CPU core.

The ME has two co-processors:

  • COP0 - general system control
  • COP1 - 32-bit Floating Point Unit

Graphics Engine[edit]

Virtual Mobile Engine[edit]

The VME appears to be one half of Sony's "Virtual Mobile Engine Concept 2" where a CPU would take care of "lightweight control tasks" and reconfigurable hardware logic (the VME) would do all of the "heavy work in a power efficient manner". See Virtual Mobile Engine - LSI that "Changes its Spots".



  • CPU and DDR are discrete ICs on the motherboard
  • 32 MiB main memory (DDR)
  • 2 MiB Media Engine memory (eDRAM)

PSP-2000 and later[edit]

  • DDR is brought into the CPU's package
  • 64 MiB main memory (DDR)
  • 4 MiB Media Engine memory (eDRAM)

See also[edit]