CPU Power State Management Latency Reduction
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Solution Overview
Problem
Current power management systems experience significant latency due to the lengthy process of transitioning a CPU from the C3/C4 state to the C0 state, which affects response times and can cause sluggish performance in applications like video playback.
Innovation Solution
Simultaneously transmitting a break event from a Southbridge to a Northbridge while transitioning the CPU from the C3/C4 state to the C0 state, and disabling the arbitrary bit to allow request transmission through the Northbridge, thereby bypassing the need for sequential state transitions and reducing latency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the CPU transitions from C3/C4 state to C0 state sequentially before processing requests, then the CPU can properly handle requests, but the request response time becomes considerably long
Solution Approach 1:
The patent applies preliminary action by transmitting the break event from Southbridge to Northbridge in advance, before the CPU completes its state transition from C3/C4 to C0. This allows the Northbridge to prepare for request routing ahead of time, reducing the overall response latency while ensuring the CPU is ready to handle requests.
Solution Approach 2:
The patent introduces a new dimension to the request processing flow by enabling parallel operations: the CPU state transition occurs simultaneously with the break event transmission through Northbridge. This dimensional change in the processing timeline allows overlapping of previously sequential operations.
2Productivity
If the arbitrary bit is disabled after CPU state transition, then requests can be transmitted through Northbridge, but this adds to the overall latency
Solution Approach 1:
The arbitrary bit is disabled in advance, before the CPU completes its state transition, allowing the Northbridge to immediately begin transmitting requests once the CPU is ready. This preliminary preparation eliminates waiting time in the request transmission path.
3Use of energy by stationary object
If the CPU remains in C3/C4 state to reduce power consumption, then energy savings are improved, but the system responsiveness deteriorates
Solution Approach 1:
The break event is transmitted through Northbridge before the CPU exits C3/C4 state, allowing the system to maintain low power consumption during the transition period while still preparing the request path in advance. This ensures minimal impact on responsiveness when the CPU does need to wake up.
Data Source
AI summary
A method of computer power state management. When an operating system thereof is idle and the processor thereof transits to a clock-suspended power state (C3/C4 state), an arbitrary bit is asserted to prevent requests from being passed through the Northbridge. When the processor is in the C3/C4 state, if a break event is received, the Southbridge transmits the break event to the Northbridge and changes the processor state from C3/C4 to C0 simultaneously. The break event is subsequently transmitted to the processor when the arbitrary bit is disabled.