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CPUs

Power Efficiency

Outline

Sandy Bridge Microarchitecture

Intel Ivy Bridge Microarchitecture

Sandy Bridge

• Focus on power efficiency enables Sandy Bridge to achieve more performance within the same TDP limits as its predecessors.
• Improvements in turbo mode enable even greater performance for short time periods.
• For notebooks this means extended battery life by completing tasks more quickly and allowing the system to revert to a sleep state.

Integration Boosts Graphics

Performance

Huge improvement in

• performance per watt

• increase the speed

of the shader engines

while reducing their

power

Integration Boosts Graphics

Performance (cont'd)

• Although programmable shaders (execution units) are area efficient, performing many different graphics functions in a single unit, fixed-function blocks are more power efficient for any given task.
• Sandy Bridge's MFX performs the entire decode process in hardware, cutting power in a half compared with previous platform
• Shifting video encoding to the GPU's media engine not only greatly reduces power but also improves

performance.

Register File Get Physical

• Previous CPUs, each instruction stores its source values in the scheduler and its result in the ROB, which copies the result to the physical register file once the instruction is retired.
• Intel decided to revert to the physical-register schema used in old Pentium 4.
• CPU implements a rename register file that is much larger than the logical register file.
• Eliminates the copying of data from ROB to physical register file, saving power.

Revving Up Turbo Mode

• Frequency of each CPU can be adjusted

individually, so it can be turned on or off as

needed.

• Sandy Bridge focus on die temperature rather

than instantaneous power dissipation.

Sandy Bridge Low Power Mobile

CPU examples

Dual Core Low Voltage CPUs

TurboBoost bumps the clock speed of the chip

during times when high performance is

demanded. By keeping the clock speed

typically much lower most of the time, the

chips can save a lot of power.

Ivy Bridge 3rd Generation

• Release Date: April 2012
• 22nm processors
• Ultra Low Voltage Models
• Destined for slim notebooks.
• Increased transistor density,

more transistors into chips

• Enhance performance &

Energy Efficiency

• 1st Intel's Tri-Gate Transistors,

Source wikipedia

Ivy Bridge

• use a nonplanar architecture to cram more transistors into less space, therefore consuming less power or delivering more performance within the same power envelope.
• Less leakage means less power consumption and less heat which is just awesome for laptop CPUs.
• This design also maximizes transistor switching performance between on and off states and decreases power-wasting leakage.

picture from intel

Ivy Bridge 3rd Generation

Power Management Improvements

• DDR I/O embedded power gating o Power off DDR I/O when in deep C states (idle)
• Configurable TDP/Low power mode
• Design optimizations to reduce S3 power
• Lower choices for System Agent operating voltages
  • Allows power optimize low power SKUs furter
• Power Aware Interrupt (PAIR)
  • Chooses 'best core' to service interrupts based on optimization mode(power vs performance)
• Optimized voltage choice for all operating frequency points
  • Best power efficiency across full range of operation

Configurable TDP/Low Power

Mode