Intel Sandy Bridge. Microarchitecture
Intel Sandy Bridge microarchitecture overview
We have already told that North Bridge logic of Sandy Bridge CPUs has been moved to a single chip together with processor cores and graphics system. With that in mind the naming for North bridge has changed to System Agent. Integrated PCIe controller supports 16 lines of PCIe 2.0, when necessary it (lines) can be split to two groups, each with 8 lines.
In addition, the power management features has been extended. System Agent includes programmable Power Control Unit, while the power itself is split into three supply groups. First group includes System Agent with all its control features. It has fixed power, while the second group (cores, the Ring and LLC) receives dynamically changing power. Power for graphics system, the third group, is also changing in reference with load applied.
Apart from extensive power management, Sandy bridge processor will have a new model of thermal management too:
Small changes in design will result in more precise temperature readings. A combination of enhanced power control and temperature monitoring opens new opportunities for automatic overclocking (Turbo boost), which is described below.
Intel Turbo Boost — it is a technology that allows the processor to run at higher (compared to default) clocks. Sandy Bridge has next gen. of Intel Turbo Boost. The main idea is simple, during overclocking, cores that stay in Idle have some time before its temperature reaches critical values. The following slide demonstrates all the processed involved in Core automatic overclocking:
In Idle, core consume minimum power, i.e. has low temperatures. When overclocked the performance curve goes up sharply, taking the TDP curve with it. On the other hand, core temperature increase smoothly allowing to run the core at higher clocks for several seconds, before reaching critical temperature value.