Processor Gather Buffer for Arbitrary-Time Unaligned Loads
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Solution Overview
Problem
Current processors handle unaligned load operations inefficiently, leading to slower performance due to rigid and inflexible handling methods such as microcode intervention or fixed timing delays, which fail to optimize memory access for unaligned loads across memory boundaries.
Innovation Solution
A gather buffer management system is implemented in the processor's load/store unit to manage unaligned load operations by temporarily storing partial writeback results in a buffer storage element and using a logic controller to track and merge these results with subsequent memory accesses at arbitrary times, allowing for flexible scheduling and efficient data retrieval.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If unaligned load operations are handled using microcode or fixed timing delays, then the operations can be completed, but processor performance deteriorates due to slower execution and rigid scheduling
Solution Approach 1:
The unaligned load operation is segmented into multiple independent memory accesses that can be executed in parallel. The load operation is divided into first and second portions, each accessed independently from memory, allowing concurrent execution and eliminating the need for sequential processing with fixed delays.
Solution Approach 2:
The system uses dynamic scheduling to determine when and how to execute the first and second memory accesses for unaligned loads. Instead of fixed timing delays, the processor dynamically schedules these accesses based on available resources and data readiness, allowing flexible optimization of execution time.
2Reliability
If multiple memory accesses are used for unaligned loads, then complete data can be retrieved, but device complexity increases due to buffer management and coordination requirements
Solution Approach 1:
The gather buffer is designed to serve multiple functions: it stores data from the first memory access, holds data from the second memory access, and facilitates merging of these data portions. This multi-functional buffer reduces the need for separate specialized structures for each function, simplifying the overall system architecture.
Solution Approach 2:
The system merges the first and second portions of data from separate memory accesses into a single complete load result. The gather buffer combines these data portions efficiently, and the execution unit merges them to produce the final unaligned load result, reducing complexity through consolidation rather than separate handling mechanisms.
3Ease of operation
If fixed timing delays are used for memory accesses, then synchronization is simplified, but adaptability deteriorates due to inability to handle arbitrary spacing between accesses
Solution Approach 1:
The system uses feedback mechanisms where the execution unit monitors the status of memory accesses and dynamically adjusts scheduling. The gather buffer receives feedback about data availability from memory, and the execution unit uses this feedback to determine when to proceed with merging operations, enabling flexible scheduling without fixed timing constraints.
Solution Approach 2:
The memory access scheduling is made dynamic rather than fixed. The system can handle arbitrary spacing between the first and second memory accesses based on data availability and processor state. This dynamic approach allows the system to adapt to different scenarios while maintaining synchronization through status tracking rather than rigid timing.
Data Source
AI summary
A computer system, processor, programming instructions and/or method for managing operations of a gather buffer for a processor core load storage unit. The processor core includes a processing pipeline having one or more execution units for processing unaligned load instructions that executes in two phases to satisfy. A buffer storage element is provided having a plurality of entries for temporarily collecting partial writeback results retrieved from the memory that are associated with first phase accesses for each of a plurality of unaligned load instructions. An associated logic controller device tracks two parts of the unaligned load to be gathered at independent times, wherein said partial result stored at said buffer storage element comprises a first part of an unaligned load. The second phase load access for the same instruction is independently accessed and later merged with first part of the load data at byte granularity to satisfy the load.