Split Reservation Station Storage for Delinquent Store Operations

Solution Overview

Problem

As computer systems become more complex, increasing the size of reservation stations to store more instructions leads to increased processor size, cost, and power consumption, and store operations can become delinquent when data is unavailable.

Innovation Solution

Implementing a secondary storage circuit for delinquent store operations and using smaller entries for certain types of operations, such as store-data entries, to increase the number of instructions stored while minimizing physical area, performance, and power consumption.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If the size of reservation stations is increased to store more instructions, then the number of stored instructions is improved, but the processor size, cost, and power consumption increase

Engineering Contradiction:

Improvenumber of stored instructionsVSAvoidpower consumption

Core Design Contradiction:

Quantity of substanceVSUse of energy by moving object

Solution Approach 1:

The reservation station is segmented into two distinct storage circuits: a primary storage circuit for active instructions and a secondary storage circuit for delinquent store operations. This segmentation allows the system to store more instructions without proportionally increasing the active storage size, thereby reducing power consumption while maintaining capacity.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The secondary storage circuit uses simplified entry structures with fewer fields compared to full reservation station entries. These reduced entries store only essential information (store address, data, and validity) rather than complete instruction metadata, effectively using 'cheaper' storage resources for delinquent operations that don't require full instruction context.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

2Quantity of substance

If the size of reservation stations is increased to store more instructions, then the number of stored instructions is improved, but the processor area increases

Engineering Contradiction:

Improvenumber of stored instructionsVSAvoidprocessor area

Core Design Contradiction:

Quantity of substanceVSArea of stationary object

Solution Approach 1:

The reservation station is segmented into two distinct storage circuits: a primary storage circuit for active instructions and a secondary storage circuit for delinquent store operations. This segmentation allows the system to store more instructions without proportionally increasing the active storage size, thereby reducing power consumption while maintaining capacity.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The secondary storage circuit uses simplified entry structures with fewer fields compared to full reservation station entries. These reduced entries store only essential information (store address, data, and validity) rather than complete instruction metadata, effectively using 'cheaper' storage resources for delinquent operations that don't require full instruction context.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

3Reliability

If store operations are kept in the reservation station waiting for data, then data availability is improved, but the store operations become delinquent and delay execution

Engineering Contradiction:

Improvedata availabilityVSAvoidexecution delay

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The secondary storage circuit acts as an intermediary between the primary reservation station and the execution unit. When store data becomes available, operations are transferred from the secondary circuit back to the primary circuit or directly issued to the execution unit, mediating the delay and reducing execution time loss.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

Store operations are prepared in advance in the secondary storage circuit with their store address and data ready, waiting only for the data to be available. This preliminary preparation reduces the time loss when data becomes available, as the operation can be immediately issued without additional setup or validation delays.

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS12461677B2Reservation station with primary and secondary storage circuits for store operations

Publication Date: 2025.11.04 APPLE INC

AI summary

A reservation station that includes primary and secondary storage circuits is disclosed. The primary storage circuit may include multiple full entries, while the secondary storage circuit includes multiple store-data entries. A given store-data entry of the multiple store-data entries stores a subset of the information stored in a given full entry of the multiple full entries. In response to a determination that a store address associated with a particular store operation, stored in particular full entry of the multiple full entries, has been available for use for a threshold number of cycles without store data associated with the particular store operation being available for use, a control circuit may transfer the particular store operation to a particular store-data entry of the multiple store-data entries.