Some thoughts on Stars improvements and Turbo Core
AMD told us that the new, improved CPU cores should be able to give over 6% better performance over the old “plain” Stars cores. Obviously this improvement, if really present, should be noticed primarily in CPU-bound operations, so we are going to analyze Llano performance in this type of benchmarks.
When we correctly measured the improvements due to microarchitectural enhancements, we can try to estimate Turbo core impact on frequency scaling. Please keep in mind that at the moment Turbo core's real operation is a bit “mysterious” as AMD didn't show a table with core utilization / Turbo P-state available, and they didn't supply an utility to see instantaneous core speed. So my estimations are, well, estimations...
From the reading of page n.339 from AMD's “BIOS and Kernel Developer’s Guide (BKDG) For AMD Family 12h Processors”,where Turbo core is called “Core Performance Boost” or CPB, (available here: http://support.amd.com/it/Processor_TechDocs/41131.pdf), and in agreement to common sense, it seems that Turbo Core technology operate in this manner:
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if a single core is utilized, try to bring up the frequency as much as permitted by the chip's estimated power consumption and thermal output
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if more than one core is utilized but no others cores are in a boosted P-state, try to bring up the frequency as much as permitted by the chip's estimated power consumption and thermal output
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if more than one core is utilized and others cores are in a boosted P-state, try to bring up the frequency as much as permitted by the chip's estimated power consumption and thermal output taking into account the additional power requirements of the others, already-boosted cores and the consequently additional heat.
The last sentence seems to left the door open to Turbo core when all cores are utilized also. However, when all cores are heavily stressed (and are outputting a lot of heat) it seems a bit unlike to me that Turbo core can really kick in, at least in current four cores APU models.
Before to go to the next page, I recap the basic hardware features of todays heroes:
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AMD A8-3850 (desktop Llano): four cores @ 2.9 GHz, no Turbo Core, 4 MB L2 cache (4x1 MB private cache), 2x64 bit DDR3-1866 memory controller, integrated Radeon 6550D (400sp, 20 TMU and 8 ROPS @ 600 MHz)
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AMD A8-3500M (mobile Llano): four cores @ 1.5 GHz (base frequency), Turbo Core at max 2.4 GHz, 4 MB L2 cache (4x1 MB private cache), 2x64 bit DDR3-1600 memory controller, integrated Radeon 6620G (400sp, 20 TMU and 8 ROPS @ 444 MHz).