Has he seen a die shot though? Maybe I'm being pedantic but surely there can be optimisations to a core that couldn't be seen on the software side. Suppose you can benchmark and compare per mhz. But I doubt performance would be identical per mhz anyway due to the differing cache setup.
Certainly seems the cores are very similar anyway. The die size seems odd for 3x Broadway cores and some SMP circuitry (and slightly more memory transistors per core) on 45nm. But I suppose shrinking a CPU to a smaller process rarely works out close to how it should theoretically.
He didn't, he's going by code efficiency and compatibility and how that doesn't seem to have changed, everything is intact and in line with a regular PPC750, taking the SMP configuration and cache aside (and SIMD features inherited from the Gekko), so, if no alarm is going off in any way it's safe for him to say it's just that; and I reckon it probably is.
Of course, he could be understimating it; new features, and new features built on top of a BC compatible platform often have to be called for specifically (otherwise the hardware will just perform as it's "supposed to"), and I'm not so sure he has access to any documentation so there's that.
It might have more SIMD intructions, somehow backported from VMX128 or specifically implemented, or we might have what Thraktor suggested, like messing with the FPU unit number and supercharging it that way; except code not expecting it, or not calling for it specifically wouldn't know that feature is there, right?
That's important because if the FPU performance was any better from the get go that could create some glitches on the BC.
It's the same principle of adding feature extensions like MMX and the like to existing platforms/technologies, if you didn't know they're there you'd never discover it by coding for it; you'd never call for them and you wouldn't know what to code for. Taking advantage of that doesn't come automagically.
On the other hand, we've heard no suggestion from anyone that actually has access to the documentation.