Out-of-order processor register renaming using standard memory maps
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Solution Overview
Problem
Conventional out-of-order processors are costly in terms of chip area, power consumption, and processing speed, limiting their applications, especially in the embedded market, due to the use of custom content-addressable memory for register renaming and other techniques.
Innovation Solution
A processor system that includes an operand renamer circuit with a register rename map, a producer tracking circuit with a producer tracking map, and a results buffer allocator circuit with a results buffer free list, which efficiently tracks the latest producer of data values and manages physical register availability to avoid hazards and serialization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional custom CAM is used for register renaming in out-of-order processors, then register renaming functionality is achieved, but chip area cost increases
Solution Approach 1:
The patent replaces the custom CAM with a register rename map that uses standard memory structures. Instead of implementing a specialized content-addressable memory hardware structure, the invention uses a tabular data structure (register rename map) that can be implemented with standard memory cells, thereby copying the functionality of CAM using more area-efficient standard components.
Solution Approach 2:
The invention substitutes the mechanical/hardware custom CAM structure with a software-managed register rename map data structure. The functionality previously requiring specialized hardware (CAM) is achieved through a structured data format that can be managed by control logic, replacing the mechanical system with a more flexible and area-efficient alternative.
2Adaptability or versatility
If conventional custom CAM is used for register renaming in out-of-order processors, then register renaming functionality is achieved, but power consumption increases
Solution Approach 1:
The patent replaces the power-hungry custom CAM hardware with a register rename map implemented using standard memory structures. This substitution copies the essential lookup functionality while dramatically reducing power consumption by eliminating the need for specialized CAM circuitry that requires continuous power for maintenance and operation.
Solution Approach 2:
The invention uses simple, easily refreshable memory structures for the register rename map instead of expensive, power-intensive CAM. The register rename map can be efficiently updated and refreshed using standard memory techniques, replacing the need for expensive, power-consuming custom CAM hardware with cheaper, more energy-efficient alternatives.
3Adaptability or versatility
If conventional custom CAM is used for register renaming in out-of-order processors, then register renaming functionality is achieved, but processing speed decreases
Solution Approach 1:
The patent pre-allocates and pre-organizes the register rename map structure before it is needed for actual renaming operations. The control logic maintains the register rename map in a ready state with all necessary entries pre-initialized, allowing for rapid lookup and updating during instruction execution without the overhead of dynamic CAM search operations.
Solution Approach 2:
The invention replaces the mechanical search operation of custom CAM with a direct addressing scheme using the register rename map. Instead of requiring complex hardware search circuits to find matching entries, the system uses straightforward index-based access to the register rename map, significantly improving access speed and reducing processing delays.
4Adaptability or versatility
If conventional out-of-order processing techniques are used, then out-of-order execution capability is achieved, but device complexity increases
Solution Approach 1:
The patent uses a universal register rename map structure that serves multiple functions: tracking producer-consumer relationships, managing physical register allocation, and maintaining in-order completion information. This single data structure replaces what would otherwise require multiple specialized hardware components, reducing overall device complexity while maintaining full out-of-order execution capability.
Solution Approach 2:
The invention merges the register renaming functionality with the results buffer management system. The register rename map is integrated with the results buffer allocater and producer tracking circuit, combining what would traditionally be separate hardware modules into a unified control structure, thereby reducing device complexity and inter-component communication overhead.
Data Source
AI summary
A processor and system for latest producer tracking In one embodiment, the processor includes an operand renamer circuit that includes a register rename map, a producer tracking circuit that includes a producer tracking map, and a results buffer allocater circuit that includes a results buffer free list. Control logic modifies in-register status values stored in the register rename map based on producer tracking status values stored in the producer tracking map. The producer tracking status values stored in the producer tracking map are modified based on buffer identification values output by the results buffer allocater circuit.