Okay, so I have quite a few results now, and I made an interesting observation - about Steamroller's performance and BIOS updates.
I first ran all of my benchmarks on my A8-7600 without modifying my system at all - same old BIOS, same old drivers, everything. I then flashed the BIOS to the BIOS with Carrizo support. I reran all benchmarks - and there was quite a jump in performance at times (as much as 13% for multi-threaded memory performance!). I think this may be due to updated code provided by AMD to BIOS vendors - and may be one of the reason why we are seeing such a wide array of performance numbers for Excavator. I will provide all these numbers, in chart form, in my upcoming
interrogation of Excavator.
Now, my old BIOS version for the FM2A88M-Extreme4+ was 2.40, from 8/15/2014. I updated to 2.90 (2/19/16) for Carrizo support. After doing so, via the UEFI, I restarted into Windows 7, the system reloaded every driver as if I had just moved the installation into a new computer - it was a drastic update, it seems. Then, today, when I installed the x4 845, and did absolutely nothing else, it happened again. Very strange. It even reloaded the graphics drivers, PCI drivers, network, USB... literally, everything.
My early results with Excavator suggest a notably more capable memory controller than Steamroller, and a not-so-consistent ~9% or so IPC advantage. I am also seeing much reduced power usage at 3Ghz (I have yet to actually do any full-speed or gaming testing).
The performance profile, though, DEFINITELY suggests that the reduced L2 capacity is hurting performance - particularly in multi-threaded scenarios. Higher frequency should help negate this more than it helped Steamroller, so I suspect Excavator may have better scaling with frequency.