“The long and short of matters then is that based on the testing we've done thus far, it doesn't look like Coffee Lake Refresh recovers any of the performance the original Coffee Lake loses from the Meltdown and Spectre fixes. Coffee Lake was always less impacted than older architectures, but whatever performance hit it took remains in the Refresh CPU design.”
Forgive me as I'm nowhere near knowledgeable in CPUs or such so my terminology will be way off.
For any CPU designed with the expectation of using the old method of memory access prediction without any protections... can we expect they'll ever show a significant performance recovery?
That is pretty obvious if you consider this is just another tweak of the venerable Skylake architecture. By now we have said good bye to the reasonable thermals we enjoyed for a while because, well, if you deliver six of the same cores that'll consume 50% more at the same clock so one hand you slow down the chip when all cores run and on another, you just allow it to consume more.
And Skylake itself wasn't a new design either, but rather a tweak of Haswell (prominent changes were in the uncore), which in turn was largely identical to SB/IB.
Skylake was a reasonably big core architecture upgrade (a "tock" in Intel terminology). Several new instructions (XSAVE, AVX512, etc.) were introduced. Perhaps you meant Broadwell?
“The long and short of matters then is that based on the testing we've done thus far, it doesn't look like Coffee Lake Refresh recovers any of the performance the original Coffee Lake loses from the Meltdown and Spectre fixes. Coffee Lake was always less impacted than older architectures, but whatever performance hit it took remains in the Refresh CPU design.”