Switch Circuitry for Memory Access Redirection
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Solution Overview
Problem
In data processing systems, there is a challenge in reducing power consumption when processing circuitry only needs to access a subset of memory locations, as existing methods require significant time and power to alter the system address map and reconfigure cache structures, leading to inefficient power savings.
Innovation Solution
The implementation of switch circuitry that intercepts access commands to unused locations in a second memory, redirecting them to unused locations in the second memory while keeping the system address map unchanged, allowing the first memory to be placed in a low power state without stalling access operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the system address map is altered and cache structures are reconfigured to enable power savings, then power consumption is reduced, but the time and power required for reconfiguration increases
Solution Approach 1:
The switch circuitry is pre-configured with address mapping information that identifies which addresses map to the first memory and which map to the second memory. This preliminary configuration allows the system to activate memory power savings by simply enabling the switch circuitry, without requiring time-consuming reconfiguration of address maps or cache structures at the time of power state transition.
Solution Approach 2:
The switch circuitry acts as an intermediary component inserted into the communication path between the processing circuitry and the first memory. It intercepts access commands and redirects them based on pre-configured address mappings, eliminating the need for the processing circuitry to be aware of or participate in the address map alteration process. This mediator approach isolates the power management function from the processing function.
2Use of energy by moving object
If the first memory is placed in a low power state, then power consumption is reduced, but access operations may be stalled or latency increased
Solution Approach 1:
The switch circuitry maintains pre-configured address mapping information that serves as a copy of the address-to-memory-location relationships. This copied information allows the switch circuitry to independently redirect access commands to the second memory without requiring the first memory to be actively powered or the address map to be dynamically updated, thus maintaining access speed while enabling power savings.
3Use of energy by moving object
If switch circuitry is inserted into the communication path to redirect access commands, then power consumption is reduced by enabling memory power down, but device complexity increases
Solution Approach 1:
The address mapping and command redirection functionality is extracted from the main processing circuitry and implemented as a separate, dedicated switch circuitry component. This extraction allows the power management function to be implemented with simple, dedicated logic rather than requiring complex general-purpose processing, thus reducing the overall complexity burden despite adding a new component.
Data Source
AI summary
An apparatus is described that has processing circuitry for performing operations, and a communication path employed by the processing circuitry to access a first memory. Switch circuitry, when activated, is connected to the communication path. The processing circuitry issues access commands specifying addresses to be accessed, where each address is mapped to location in a memory system in accordance with a system address map. The memory system comprises at least the first memory and a second memory. When in a particular mode, the processing circuitry performs operations that require access to only a subset of the locations provided in the first memory. The switch circuitry is arranged, whilst the processing circuitry is in the particular mode, to be activated in order to intercept the access commands issued over the communication path that specify addresses mapped by the system address map to locations within the subset of locations. Those intercepted access commands are redirected to locations within the second memory that are otherwise unused whilst the processing circuitry is in the particular mode. This can provide significant power consumption benefits.