Simplified State Machine for I/O Value Prediction
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Solution Overview
Problem
Current processor systems face long latencies when interacting with I/O devices due to the inability to optimize load, store, and atomic requests using normal cache techniques, leading to suboptimal performance in accessing data from I/O devices.
Innovation Solution
A processor core employs a simplified state machine with reduced state transition logic to predict I/O device state values, allowing for improved instruction execution performance by omitting unnecessary requests to I/O devices and efficiently managing state values associated with I/O instructions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the processor uses normal cache techniques for I/O requests, then the cache structure can be simplified, but the instruction execution latency increases due to inability to optimize I/O access
Solution Approach 1:
The patent segments the I/O access optimization by creating a separate prediction structure (simplified state machine) independent from the main cache hierarchy. This segmented approach allows the prediction logic to operate in parallel with I/O requests, providing predicted values without requiring complex modifications to the existing cache structure, thus reducing both complexity and latency.
Solution Approach 2:
The patent introduces an intermediary prediction structure (simplified state machine) that mediates between the processor core and the I/O device. This intermediary predicts I/O device state values and provides them to the processor core, eliminating the need for complex cache optimizations while reducing instruction execution latency through predicted values.
2Measurement precision
If the processor sends all I/O requests to the I/O device, then the I/O device can provide accurate state values, but the instruction execution performance deteriorates due to long latencies
Solution Approach 1:
The patent applies preliminary action by having the simplified state machine predict I/O device state values in advance before actual I/O requests are completed. The prediction structure proactively computes anticipated state values based on current state and transition logic, allowing the processor core to receive predicted values immediately without waiting for slow I/O device responses, thus maintaining productivity while preserving accuracy through validation mechanisms.
Solution Approach 2:
The patent changes the parameter of state value acquisition from synchronous (waiting for I/O device) to asynchronous (predicted values). The simplified state machine operates with different timing parameters, generating predicted state values independently of the slow I/O device response time, thereby improving instruction execution performance while maintaining accuracy through subsequent validation against actual I/O device states.
3Productivity
If the processor creates an accurate simplified state machine to predict I/O device state, then the instruction execution performance improves, but the controller complexity increases
Solution Approach 1:
The patent creates a simplified copy (simplified state machine) of the I/O device's state transition logic rather than implementing a fully accurate complex model. This copy captures the essential prediction functionality with reduced complexity, allowing the controller to predict I/O device state values effectively without becoming overly complex, thus improving instruction execution performance while maintaining manageable controller complexity.
4Loss of time
If the processor omits forwarding requests to the I/O device using prediction, then the latency is reduced, but the prediction accuracy may deteriorate leading to incorrect state values
Solution Approach 1:
The patent implements feedback mechanisms where the actual I/O device state values are compared with predicted values. When discrepancies are detected, the system can invalidate or update the prediction structure to maintain accuracy. This feedback loop allows the processor to omit forwarding requests and use predicted values (reducing latency) while maintaining prediction accuracy through continuous validation and correction.
Data Source
AI summary
An apparatus, and corresponding method, for input/output (I/O) value determination, generates an I/O instruction for an I/O device, the I/O device including a state machine with state transition logic. The apparatus comprises a controller that includes a simplified state machine with a reduced version of the state transition logic of the state machine of the I/O device. The controller is configured to improve instruction execution performance of a processor core by employing the simplified state machine to predict at least one state value of at least one I/O device true state value to be affected by the I/O instruction at the I/O device.