Concurrent Complex-Instruction Decode for Variable Output Width
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Solution Overview
Problem
Modern processors face inefficiencies in decoding complex instructions, particularly those with varying numbers of decoded instructions, which can lead to performance bottlenecks and increased latency due to the need for specialized decode circuitry that is either too general or too specialized, leading to contention and reduced throughput.
Innovation Solution
The implementation of concurrent decoding mechanisms using a combination of Programmable Logic Array (PLA) based decode circuitry for repetitive and simple instructions, and shared Read-Only Memory (ROM) based decode circuitry for more complex and irregular instructions, allowing for parallel processing of different types of complex instructions, thereby optimizing decode throughput.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If specialized decode circuitry is used for complex instructions, then decoding accuracy is improved, but device complexity and area increase
Solution Approach 1:
The decode circuitry is segmented into multiple specialized decode units, each handling specific types of complex instructions. This segmentation allows each unit to be optimized for its specific function while avoiding the need for a single overly complex general-purpose decoder, thus improving decoding accuracy without proportionally increasing overall device complexity.
Solution Approach 2:
The decode circuitry is designed with multi-functional capabilities where decode units can handle multiple types of instructions. This universality allows the system to maintain high decoding accuracy for complex instructions while reducing the total number of specialized units needed, thereby controlling device complexity and area.
2Device complexity
If general-purpose decode circuitry is used, then device complexity is reduced, but decoding speed and throughput decrease
Solution Approach 1:
The decode circuitry is divided into multiple parallel decode units that can simultaneously decode different instructions. This segmentation enables the system to maintain low individual unit complexity while achieving high overall throughput through parallel processing, resolving the contradiction between simplicity and productivity.
Solution Approach 2:
The system transitions from sequential decoding to parallel decoding by adding temporal and spatial dimensions to the decode process. Multiple decode units operate concurrently, effectively increasing throughput without requiring each individual unit to be overly complex, thus maintaining simplicity while improving productivity.
3Productivity
If more decode units are added to handle varying numbers of decoded instructions, then decode throughput is improved, but area and power consumption increase
Solution Approach 1:
Decode units are designed with universal capabilities to handle multiple types of complex instructions with varying numbers of decoded instructions. This multi-functionality allows the system to achieve high throughput with fewer units, reducing the total area required compared to having separate specialized units for each instruction type.
Solution Approach 2:
The decode units are designed to dynamically adapt their output based on the input instruction characteristics. By changing operational parameters rather than hardware configuration, the system can handle varying instruction complexities with the same physical units, optimizing area utilization while maintaining high throughput.
4Measurement precision
If specialized decode circuitry is implemented for each complex instruction type, then decoding precision is improved, but manufacturing cost increases
Solution Approach 1:
The patent implements universal decode units that can handle multiple complex instruction types through software or configuration rather than requiring separate hardware for each instruction type. This approach maintains high decoding precision while significantly reducing manufacturing complexity and cost compared to fully specialized circuitry.
Solution Approach 2:
Instead of creating unique specialized circuitry for each complex instruction type, the system uses replicated universal decode units that can be configured to handle different instruction types. This copying approach maintains precision through proper configuration while reducing manufacturing costs by using standardized reusable units.
Data Source
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AI summary
A processor of an aspect includes decode circuitry to decode a first subset of instructions and a second subset of instructions. The decode circuitry is to concurrently decode at least two instructions of the first subset of instructions. The first subset of instructions is to be decoded into varying numbers of decoded instructions ranging from at least two to at least ten. The decode circuitry is only able to decode fewer instructions of the second subset of instructions at a time than the at least two instructions of the first subset of instructions. Each of the second subset of instructions is to be decoded into at least two decoded instructions. The processor also includes circuitry coupled with the decode circuitry to receive decoded instructions from the decode circuitry. Other processors, methods, systems, and instructions are disclosed.