Multi-indexed Micro-operations Cache for Processor Instruction Retrieval
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Solution Overview
Problem
Existing computer systems face challenges in efficiently decoding and executing multiple instructions due to limitations in processor caching mechanisms, leading to increased latency and power consumption.
Innovation Solution
The proposed solution involves an apparatus with a decode unit and a micro-operations cache, where the decode unit decodes instructions into micro-operations and the micro-operations cache stores these micro-operations along with identifiers and location indications, enabling efficient retrieval and execution of instructions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If instructions are decoded and stored in a traditional micro-operations cache with single indexing, then the cache structure is simple, but retrieval latency increases and execution efficiency decreases when multiple instructions need to be accessed
Solution Approach 1:
The cache tag array is segmented into multiple index fields (first index field, second index field, third index field) that can independently identify different instructions. Each tag entry contains multiple intermediate entries corresponding to different index combinations, allowing the cache to store and retrieve multiple instruction sets simultaneously without requiring a completely new cache architecture.
Solution Approach 2:
The patent introduces multi-dimensional indexing by adding multiple index fields beyond the traditional single index. This transforms the cache addressing from one-dimensional to multi-dimensional, enabling simultaneous access to multiple instruction sets stored in the same cache line through different index combinations, thereby improving execution efficiency without proportionally increasing physical cache size.
2Quantity of substance
If the micro-operations cache stores multiple instruction sets in the same cache line, then cache utilization improves, but the complexity of storing and retrieving metadata increases
Solution Approach 1:
The tag array entries are designed to serve multiple functions: they store the primary instruction identifier, multiple intermediate entries for different index combinations, and validity bits. This multi-functional design allows the same cache structure to handle both single and multi-instruction retrieval scenarios without requiring separate metadata structures, thereby improving cache utilization while controlling metadata complexity.
Solution Approach 2:
The patent implements a nested structure where intermediate entries are embedded within tag array entries. Each tag entry contains a primary identifier and nested intermediate entries that reference the same cache line through different index combinations. This nesting allows compact storage of multiple instruction references within the same metadata structure, improving cache utilization without linearly increasing metadata size.
3Ease of manufacture
If traditional caching mechanisms are used for instruction retrieval, then the system is easy to implement, but power consumption increases due to repeated decoding and fetching
Solution Approach 1:
The cache pre-stores multiple instruction sets and their corresponding metadata (tag entries with intermediate entries) during idle periods or when cache space is available. When execution needs arise, the pre-stored instructions can be retrieved immediately through multi-indexed access without requiring repeated decoding or fetching from higher-level caches, thereby reducing power consumption while maintaining implementation simplicity.
Data Source
AI summary
Various example embodiments for supporting a multi-indexed micro-operations cache (MI-UC) in a processor are presented. Various example embodiments for supporting an MI-UC in a processor may be configured to support an MI-UC in which, for a UC line of the MI-UC, multiple indexes into the UC line, for multiple sets of micro-operations (UOPs) stored in the UC line based on decoding of multiple instructions, are supported.