Tachyon

PSP CXD2962GG

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"

See Allegrex.

Media Engine

See Media Engine.

Graphics Engine

See main article: Graphics

Virtual Mobile Engine

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".

It might be something like a reconfigurable DSP; noone has been able to interpret its "firmware" yet.

It can be accessed from the ME through the mfvme/mtvme instructions or through DMA with addresses from 0x440F8000 to 0x44100000 (excluded).

Memory mapping

This memory mapping is shared by the SC, the GE & the ME, except the VRAM which is accessible only by the SC and the GE.

Start	End	Size	Description
0x00010000	0x00013FFF	0x00004000 (16KiB)	Allegrex Scratchpad
0x04000000	0x041FFFFF	0x00200000 (2MiB)	Graphics Engine VRAM
0x08000000	0x087FFFFF	0x00800000 (8MiB)	Allegrex Kernel memory (RAM)
0x08800000	0x09FFFFFF	0x01800000 (24MiB)	Allegrex User memory (RAM)
0x1C000000	?	?	Hardware registers
0x1FC00000	0x1FDFFFFF	0x00200000	MIPS Reset Vector
0x1FE00000	?	?	Hardware registers

See Hardware Registers for details about the hardware registers.

Access can be cached & privileged or not by changing the first 4 bits (31-28 bits) of the address using this virtual memory mapping:

Address	Name	Is it cached?	Permission	Description
0x00000000	KU0	Cached	User/Supervisor/Kernel	Main memory
0x40000000	KU1	Uncached	User/Supervisor/Kernel	Often used for VRAM
0x80000000	K0	Cached	Kernel	Main kernel memory
0xA0000000	K1	Uncached	Kernel	Mainly used for hardware registers
0xC0000000	K2/KS	Cached	Supervisor/Kernel	Usage unknown/unconfirmed
0xE0000000	K3	Cached	Kernel	Usage unknown/unconfirmed

PSP-1000 VFPU bug

PSP-1000 CPU has broken ulv.q instruction, that causes FPU registers corruption.

You can see more about it here.

Versions

PSP-1000

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

See also

• https://www.zdnet.com/article/sony-reveals-some-specs-for-psp-handheld/ (2004)

• https://www.extremetech.com/extreme/56942-sony-details-psp-chip-specs

• https://www.copetti.org/writings/consoles/playstation-portable/