The ME sees the main CPU's RAM, but has its own eDRAM at 0 (with
0x80000000 and 0xA0000000 mirrors) where the main CPU has its scratchpad,
its own memory where the main CPU has VRAM, and both CPUs share the boot
page at 0xBFC00000.
- The ME's own memory is views in the main arena flagged MV_ME_ONLY, which
only Memory::CreateMESpace() maps, into a second reservation along with
the shared views at their same arena positions. It gets its own block
shadow.
- The eDRAM (MV_EDRAM) is the ME's half of the eDRAM chip, the GE's VRAM
being the other: 2MB on the PSP-1000 (whose resident ME image says so),
4MB on the others (from mcidclan's libmecore, not hardware-checked).
- At VRAM's addresses, through 0x44000000 and 0xA4000000 alike, the ME
doesn't see VRAM but memory of its own (pspautotest me/vram, on a
PSP-1000): where homebrew keeps the VME's buffers. Its size isn't known;
2MB with VRAM's mirrors here, and no depth layout on 16-bit accesses.
- 0xA0000000 reaches physical memory uncached, so RAM is mapped at
0xA8000000 too.
- The boot page is a view too, which the main CPU reaches through a new
MMIO device (in savestates from MMIO section version 2). The ME runs
code from it, uncached, so the main CPU's writes invalidate code there.
On masked platforms it isn't mapped, and the device uses a plain
buffer.
- AddressSpace has IsValidAddress etc, with the ME's rules when edramSize
is set, and the interpreters and the IR interpreter check and fetch
instructions through their state's space. The IR compiler's checks still
use the main CPU's, until the ME gets a JIT.
- On Darwin, MemArena can hold several view reservations.
Masked platforms (iOS, 32-bit) don't get an ME space yet.
Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
