Given the timeframe and the negligible die size, it'll nearly certainly be a Cortex-A9 at 600MHz+ with a plain FPU (no NEON) and a moderately sized L2 cache, probably 256KiB. FWIW, that would make it faster than any other handheld in the world today that I'm aware of, but that's more of a testament to ARM and Moore's Law than Nintendo. Here we're talking about an entire CPU subsystem that costs ~$1 to make...
It is interesting to point out that I find MIPS' CPU roadmap to be noticeably less impressive than ARM's. If Sony does choose to remain on the MIPS road for PSP2 (what choice do they really have? CELL-like? Puh-lease. And that's just asking for trouble anyway), then that might prevent them from achieving a real raw CPU performance advantage this generation; although honestly the bottleneck would presumably be the GPU anyway (and both systems will nearly certainly have OpenGL ES 2.0 GPUs)
CELL-like... why not ?
It does not have to have complete ISA compatibility on the PPU-side, but you could keep (if it launched at 45 nm) the SPE's the way they are and you might get away with something simplier than the fat EIB since you'd have less and much lower clocked SPE's.
You'd still gain by keeping SPU compilers and tuned tools, including all the SPU optimized OS code (reserved isolated mode SPU, etc...) and you'd just need to port the rest of the XMB Game OS to the new PPU (which might be an ARM, or a smaller/modified PowerPC core, etc...).
SPE's EVERYWHERE!
Low learning curve for PS3 developers and yet another reason for developers to learn how to code for SPU's.
I think that at 45 nm the impact of a CPU-core + 4 SPE's (1 reserved for system use) clocked between 400-600 MHz and paired with a PowerVR SGX GPU connected through the FlexIO bus would be quite interesting.
Make the FlexIO connection fast enough, use XDR/XDR-2 (800-1,200 MHz effective data rate or 100-150 MHz base clock), or mobile DDR as main RAM... have the SGX read and write to it... UMA-style if you can
.
That would give you 6.4-9.6 GB/s of main RAM bandwidth given a dual channel, 32 bits x channel, XDR1 set-up.
Compared with 2.5 GB/s for PSP it is already quite a nice upgrade... and don't TDBR's need low external bandwidth anyways
.
ok... ok... need more time to tweak these paper specs
.