4 ms·
Conclusion at the end is fairly brutal: “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
by MR4D 8y ago
Conclusion at the end is fairly brutal:
“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.”
- duxup 8y agoForgive 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? I guess I always assumed the answer was no.
- ethbro 8y ago(Someone please correct me if I'm wrong) Without adding additional hardware, likely not significant. The way you avoid some of the impacted scenarios (at modest performance impact) is with additional hardware or microarchitecture changes. Basically, the task is 'Ensure processor state, as observed by another process, never changes because of speculative execution branches.' Which is a high bar to meet, especially if you want to simultaneously optimize your execution unit utilization.
- chx 8y agoThat 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.
- blattimwind 8y agoAnd 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.
- dantle 8y agoSkylake was a reasonably big core architecture upgrade (a "tock" in Intel terminology). Several new instructions (XSAVE, AVX512, etc.) were introduced. Perhaps you meant Broadwell?
- wtallis 8y agoConsumer Skylake and derivatives didn't get AVX512; that's reserved for the server parts that arrived two years later.
- chx 8y agoIt's been benchmarked that from Sandy Bridge to Kaby Lake the IPC only grew 20% https://www.hardocp.com/article/2017/01/13/kaby_lake_7700k_vs_sandy_bridge_2600k_ipc_review/4 https://www.hardocp.com/article/2017/01/13/kaby_lake_7700k_v... but the power efficiency has brutally increased: This is a 35W CPU in 2011 https://browser.geekbench.com/processors/381 https://browser.geekbench.com/processors/381 and this is an Y (4.5-7W) CPU from 2017 https://browser.geekbench.com/processors/1822 https://browser.geekbench.com/processors/1822 .