The System Agent
Altered principally in name, the system agent includes functionality previously associated with the uncore—that is, it includes the processor subsystems that can’t be grouped with the execution cores (and now the graphics engine, too).
In that list, you have the dual-channel memory controller (which officially supports transfer rates of up to 1333 MT/s), 16 lanes of second-generation PCI Express connectivity, the DMI, and a more advanced power control unit, responsible for managing the operation of Turbo Boost, among its other roles.
Turbo Boost 2.0?
Speaking of Turbo Boost, Sandy Bridge includes a second-generation implementation of this technology, first seen two years ago on Bloomfield-based Core i7-900-series chips, but really only throttled up, so to speak, on Lynnfield a year later.
The premise behind what I’ll call Turbo Boost 1.0 was that, in a multi-core CPU, available resources are not always in use. An application like iTunes, for instance, can only use one core at a time. And yet, the chip’s thermal ceiling is defined by a worst-case scenario of all cores fully-utilized. Turbo Boost takes advantage of the thermal headroom that exists when the chip executes a workload like iTunes, in turn accelerating the one active core to get its task completed faster.
Turbo Boost 1.0 is smart in that it dynamically ratchets up the frequency of active cores based on temperature, current, power consumption, and operating system states. But it won’t exceed programmed power limits, even if thermal headroom exists to push performance harder.
In the real-world, a processor doesn’t heat up right away, though. From idle, it takes time to reach its thermal ceiling. Turbo Boost 2.0 (or next-gen Turbo Boost, whatever you want to call it) allows the processor to exceed its power ceiling until it reaches its thermal limit, at which point it drops power to conform to those same programmed limits.
Turbo Boost 2.0 does not mean the CPU will exceed its maximum Turbo Boost frequency. If you have a Core i7-2600K with a 3.4 GHz base clock and 3.8 GHz maximum Turbo clock, 3.8 is as fast as it’ll go in its stock trim. It’ll simply stay there longer—until the CPU heats up to its thermal limit—before backing down.
Unfortunately, it’s not really possible to quantify the benefits of this capability. The best I could get out of Intel was that it helped improve responsiveness. On the desktop, I frankly wasn’t able to tell a difference, and as a result, Turbo Boost 2.0 comes across somewhat gimmicky.
To be fair, it’s going to mean more in the mobile space, where base clocks start off a lot lower to save power, and Turbo Boost ceilings scale significantly higher. We have a Sandy Bridge-based notebook in the office and will be putting it through its pages this month, too.
Also more impactful in the mobile space is Sandy Bridge’s ability to share thermal budget between graphics and processor cores. Previous-generation Arrandale cores were able to do this, applying the Turbo Boost concept to both components. Now Sandy Bridge enables the same capability on the desktop. Intel says that, in 3D-heavy workloads, the power control unit will bias to the graphics core, as it stands to improve performance more than faster CPU cores.
- Core i7-2600K, Core i5-2500K, Core i5-2400, And Core i3-2100 Reviewed
- Inside Of Sandy Bridge: Cores And Cache
- The System Agent And Turbo Boost 2.0
- Sandy Bridge’s Secret Weapon: Quick Sync
- Quick Sync Vs. APP Vs. CUDA
- Blu-ray Playback And Video Performance
- HD Graphics On The Desktop: Intel Trips Up
- Two New Platforms, More On The Way
- Overclocking: Sandy Bridge Changes The Game
- Meet Intel’s Second-Gen Core CPUs
- Hardware Setup
- Benchmark Results: PCMark Vantage
- Benchmark Results: 3DMark11
- Benchmark Results: SiSoftware Sandra 2011
- Benchmark Results: Content Creation
- Benchmark Results: Productivity
- Benchmark Results: Media Encoding
- Benchmark Results: Metro 2033 (DX11)
- Benchmark Results: F1 2010 (DX11)
- Benchmark Results: Aliens Vs. Predator (DX11)
- Benchmark Results: Power Consumption