Unified Speculation Matrix for Scalable Processor Reservation Stations
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Solution Overview
Problem
Current processor designs face challenges in scaling the number of reservation station entries and dispatch ports due to single cycle timing path pressure, RC delay, and the need for additional comparators, which degrades performance and increases power and area costs, especially when implementing dynamic port binding schemes.
Innovation Solution
A scalable reservation station circuit with a unified speculation state propagation and execution wakeup matrix, combined with a true age-based dynamic port-binding pick-2 scheduler, allows for doubling the number of dispatch and execution ports without introducing additional single cycle timing paths, using execution circuit clustering and eliminating the need for costly load dependence matrices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the number of reservation station entries and dispatch ports is increased to improve execution bandwidth, then processor performance is improved, but single cycle timing path pressure and RC delay increase causing performance degradation
Solution Approach 1:
The reservation station is divided into multiple sets, with each set having its own dedicated execution ports. This segmentation allows the timing paths to be distributed across multiple smaller units rather than one large unit, reducing the RC delay and timing pressure in each individual path while maintaining overall high execution bandwidth through parallel operation of multiple sets.
2Adaptability or versatility
If additional comparators are added to support dynamic port binding schemes, then port binding flexibility is improved, but device complexity and power consumption increase
Solution Approach 1:
The port binding logic and comparison functions are merged into the unified speculation state propagation and execution wakeup matrix circuit. This integration eliminates the need for separate comparator circuits, reducing overall device complexity and power consumption while maintaining the flexibility of dynamic port binding through the unified matrix structure.
3Reliability
If separate load dependence matrices are implemented to track load speculation, then speculation tracking accuracy is improved, but power consumption and area costs increase
Solution Approach 1:
The unified speculation state propagation and execution wakeup matrix circuit performs multiple functions: it tracks load speculation, propagates speculation states, and generates execution wakeup signals. This multi-functional approach eliminates the need for separate load dependence matrices, reducing power consumption and area costs while maintaining speculation tracking accuracy through the integrated matrix structure.
Data Source
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AI summary
Systems, methods, and apparatuses relating to a scalable reservation station circuit implementing a single unified speculation state propagation and execution wakeup matrix in a processor are described. In one embodiment, a hardware processor core includes a decoder circuit to decode one or more instructions into a first micro-operation to load data from a data cache, a second micro-operation dependent on the first micro-operation, and a third micro-operation dependent on the second micro-operation; an execution circuit to execute the first micro-operation, the second micro-operation, and the third micro-operation; and a reservation station circuit comprising a load speculation tracker circuit and coupled between the decoder circuit and the execution circuit, the load speculation tracker circuit to, for a reservation station entry of the third micro-operation, track progress of the first micro-operation in the data cache to generate a cancellation indication for the third micro-operation in response to a miss of the data in the data cache for the first micro-operation, wherein the load speculation tracker circuit is to begin to track the progress of the first micro-operation in the data cache in response to a dispatch of the first micro-operation into the data cache..