Editing CPU

Tachyon is the codename for the main CPU of the PSP.

Tachyon has one primary CPU core which is responsible for running the XMB and games, and a second CPU core which implements the audio and video decoding functionality of the PSP.

[[File:PSP CXD2962GG.jpg|thumb|left|PSP CXD2962GG]]<br>
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=== Specifications ===
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 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.

== Main Core "SC" ==
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 main CPU has an internal 16 KiB of scratchpad RAM that is accessed directly without going through the system bus.

== Mobile Engine "ME" ==
The Mobile 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
*COP2 - Vector Floating Point Unit

The ME 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 [https://www.yumpu.com/en/document/read/10961029/virtual-mobile-enginetm-vme-sony Virtual Mobile Engine - LSI that "Changes its Spots"].

== Versions == 
=== PSP-1000 ===
*CPU and DDR are discrete ICs on the motherboard
*32 MiB main memory (DDR)
*2 MiB Video memory (eDRAM)
*2 MiB Media Engine memory (eDRAM)

=== PSP-2000 and later ===
*DDR is brought into the CPU's package
*64 MiB main memory (DDR)
*4 MiB Video memory (eDRAM)
*4 MiB Media Engine memory (eDRAM)