Block-Based Processor Nullification for Energy Efficiency
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Solution Overview
Problem
Current processor architectures, such as RISC designs, face limitations in performance improvement due to increased complexity and energy consumption, particularly in managing instruction-level parallelism and out-of-order execution, which hinders further gains in transistor scaling and efficiency.
Innovation Solution
The implementation of block-based processor architectures with explicit data graph execution (EDGE) ISAs, which organize instructions into atomic blocks for efficient execution, reducing the need for complex architectural features like register renaming and misspeculation recovery, and utilizing nullification instructions to manage predicated execution paths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If out-of-order superscalar implementations are used to improve processor performance, then instruction-level parallelism increases, but device complexity and energy consumption increase
Solution Approach 1:
The processor divides instructions into fixed-size atomic blocks that execute together as a unit. This segmentation simplifies the control logic by eliminating the need for complex out-of-order execution mechanisms, register renaming, and misspeculation recovery, while maintaining high instruction-level parallelism through block-level parallelism.
Solution Approach 2:
Instead of executing instructions out-of-order as in traditional superscalar processors, this architecture executes blocks of instructions in a simplified order, using predicated execution to handle conditional logic. This inversion of the execution model reduces complexity while preserving performance benefits.
2Productivity
If predicated execution paths are implemented to improve performance, then instruction efficiency increases, but device complexity increases due to nullification requirements
Solution Approach 1:
The architecture creates shadow copies of register files and memory structures to track both possible execution paths simultaneously. When a predicated instruction is executed, the non-taken path's effects are nullified by comparing with the shadow copy, eliminating the need for complex rollback mechanisms while maintaining simple control flow.
3Productivity
If transistor scaling continues to improve performance, then clock frequency and energy efficiency increase, but manufacturing benefits are slowing or reversing
Solution Approach 1:
The architecture changes fundamental operational parameters by using fixed-block instruction execution with predicated operations instead of traditional out-of-order execution. This parameter change enables simpler circuit designs that are more amenable to manufacturing scaling, while maintaining high energy efficiency through reduced control logic and fewer transistors per operation.
Data Source
AI summary
Apparatus and methods are disclosed for nullifying memory store instructions and one or more registers identified in a target field of a nullification instruction. In some examples of the disclosed technology, an apparatus can include memory and one or more block-based processor cores configured to fetch and execute a plurality of instruction blocks. One of the cores can include a control unit configured, based at least in part on receiving a nullification instruction, to obtain an instruction identification for a memory access instruction of a plurality of memory access instructions and a register identification of at least one of a plurality of registers, based on a first and second target fields of the nullification instruction. The at least one register and the memory access instruction associated with the instruction identification are nullified. Based on the nullified memory access instruction, a subsequent memory access instruction is executed.