Media Engine

The Media Engine (or shortly 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".

Overview

The ME runs at the same clock frequency as the main CPU core. It seems to have the same instruction set.

The ME has two co-processors:

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

It has three instructions the main CPU doesn't have (or used):

• DBREAK (also present on other MIPS processors): used only once in the ME firmware
• MTVME
• MFVME

These two last instructions actually have the same opcodes as LDL and SDL, which this CPU doesn't have. The instructions are actually encoded like this:

 ldl $reg, off($a3) <=> mfvme $reg, $off
 sdl $reg, off($a3) <=> mtvme $reg, $off

They might be used to store and retrieve information from and to the VME. They seem to be only used for video decoding.

Memory mapping

Start	End	Size	Description
0x00000000	0x001FFFFF	0x00200000 (2MiB)	ME Memory
0x04000000	0x041FFFFF	0x00200000 (2MiB)	Graphics Engine VRAM
0x040F8000	0x04100000	0x00008000 (32KiB)	VME Memory (Need confirmation, collide with GE mem)
0x08000000	0x087FFFFF	0x00800000 (8MiB)	Allegrex Kernel memory (RAM) (ME program is loaded at 0x8300000 - 0x837FFFF)
0x08800000	0x09FFFFFF	0x01800000 (24MiB)	Allegrex User memory (RAM)
0x1C000000	?	?	Hardware Registers
0x1FC00000	0x1FDFFFFF	0x00200000	MIPS Reset Vector

Software

New ME binaries are carefully stripped from any debug info. But old version has few debug strings and even some function names. Example strings from 1.02 devkit firmware from ME program dedicated to UMD Video playback.

• Mangled names

ROM:08300000 TACHYON
ROM:083358AC pure virtual method called\n
ROM:083377C0 14PictListBField
ROM:083377D4 14PictListPField
ROM:083377E8 14PictListBFrame
ROM:083377FC 14PictListPFrame
ROM:08337810 13ReferenceList
ROM:08337898 8PocType2
ROM:083378A4 8PocType1
ROM:083378B0 8PocType0
ROM:083378E0 3Poc
ROM:083379B0 13PictListField
ROM:083379C0 13PictListFrame
ROM:083379D0 20RefFrameListLongTerm
ROM:083379E8 23RefFrameBList1ShortTerm
ROM:08337A04 23RefFrameBList0ShortTerm
ROM:08337A20 23RefFramePList0ShortTerm
ROM:08337A70 18ReferenceFrameList
ROM:08337A90 6squeueI5FrameLi4EE
ROM:08337BCC N10__cxxabiv121__vmi_class_type_infoE
ROM:08337BF4 N10__cxxabiv120__si_class_type_infoE
ROM:08337C1C N10__cxxabiv117__class_type_infoE
ROM:08337C40 St10bad_typeid
ROM:08337C50 St8bad_cast
ROM:08337C5C St9type_info
ROM:08337CB4 St13bad_exception
ROM:08337CC8 St9exception
ROM:08337CFC St9bad_alloc

• Version info:

AVCDEC SW_VER_1_08 ES_RTL
tkimura@avnpb
2004/10/26,15:14:55
/usr1/tkimura/Work/A1RING/A1RING_SOFT/Tools/BuildTools