What
could make sense to me is more something like this.
An APU may indeed not provide the power Sony wants with the a given silicon budget and power budget.
Sony is not pleased by the power profile of either trinity or even the up coming Kaveri desktop parts and what they achieve within that power profile.
Bobcat replacement the jaguar cores don't suck too much and within the silicon and power budget of Sony are a better fit.
Sony doesn't want to go with chips either too big or too hot.
Sony view Pitcairn for what it is: impressive either wrt to its size, power profile and performance.
They decided to go (from the number of SIMD) that could be named a HD7870LE or hd7860 (or the HD8xxx equivalent)
I would bet it's going to be clocked conservatively (below 800MHz) and then let AMD power tuning thing adjust the GPU to match a defined TDP. 100 Watts is a maximum.
800MHz may be the max speed as it matches the rumored FLOPS counts (and it makes sense to communicate on peak figures).
The chip is going to be tweaked and act as the north bridge (ala Xenos)
The chip will support a 256bit bus connected to fast gdd5. 2Gb of RAM, Sony evaluates the possibility/doability to move to 4GB.
The Apu is going to be around the same size as the GPU ~200 sq.mm
Moving from stream roller cores to Jaguars, I would think Sony would go with more than 4 cores.
I could see the CPU and CU count being anywhere between 4 and 8.
I could see 6 cpu cores and 6 CU as being "sane". ( I may favor 8 cpu cores and 4 SIMD. tho).
I can see the cpu cores max clock speed being 2.4GHz and the GPU being 800Mhz. then turbo does it job to keep the chip within the tdp.
The APu is connected to the GPU/North bridge using PCix3 and has 32GB/s of bandwidth to play with (a bit less with the coherency traffic).
Both chip used TSMC 28nm process.
I could see the TDP of both chip being set @80Watts.
The 7970 is used in dev kit, it's convenient lot of head room in perfs, multiple ACE may help to emulate the APU running parallel form the GPu from example, etc.
Overall the system embark 24 CU operating in the best case scenario (so when tdp allows) at 800Mhz. The peak FLOPS figure would be just below 2.5TFLOPS for the system as a whole.