MSR Write Serialization Control for Lower Processor Latency

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Solution Overview

Problem

Modern processors face performance penalties due to the architecturally serializing nature of the WRMSR instruction for writing Model Specific Registers (MSRs), which is not necessary for all MSRs, leading to increased latency and complexity in identifying and handling non-serializing MSRs.

Innovation Solution

A non-serializing write instruction (WRMSRNS) is introduced to minimize latency by ensuring that only the necessary serialization is applied based on the specific state being updated, allowing the processor to execute MSRs with minimal latency and functional correctness.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the WRMSR instruction is used to write Model Specific Registers, then architectural serialization is ensured for all MSRs, but latency increases and performance decreases

Engineering Contradiction:

Improvearchitectural serializationVSAvoidinstruction latency

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The patent segments the MSR write operation into two distinct instruction types: WRMSR for serializing writes and WRMSRNS for non-serializing writes. This segmentation allows software to selectively apply serialization only when needed, rather than forcing all MSR writes to be serialized, thereby reducing unnecessary latency while maintaining architectural correctness where required.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent introduces dynamic behavior to the MSR write mechanism by providing two instruction variants that can be chosen based on the specific requirements of the operation. The WRMSRNS instruction dynamically bypasses the serialization pipeline when full serialization is not needed, allowing the system to adapt the level of serialization to the actual requirements of each MSR write operation.

Inventive Principle:

Principle #15Dynamics

2Loss of time

If non-serializing MSRs are specially identified and handled, then latency is reduced for those specific registers, but device complexity and detection logic increase

Engineering Contradiction:

ImproveMSR write latencyVSAvoiddetection and handling logic

Core Design Contradiction:

Loss of timeVSDevice complexity

Solution Approach 1:

Instead of creating complex detection logic to identify which MSRs are non-serializing, the patent inverts the approach by providing a unified WRMSRNS instruction that treats all MSRs as potentially non-serializing. The serialization behavior is then determined by the instruction type rather than by complex runtime detection of MSR properties, significantly simplifying the hardware logic while maintaining the ability to achieve low-latency writes.

Inventive Principle:

Principle #13The other way round (Inversion)

3Adaptability or versatility

If each non-serializing MSR is enumerated for software, then special handling is enabled, but custom enabling logic and documentation costs increase

Engineering Contradiction:

Improvespecial case handlingVSAvoidenabling logic and documentation

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent creates a universal WRMSRNS instruction that can be applied to any MSR without requiring software to know which specific registers are non-serializing. This universal approach eliminates the need for enumerating individual non-serializing MSRs, removing the associated complexity of custom enabling logic and extensive documentation while maintaining full adaptability for performance-critical applications.

Inventive Principle:

Principle #6Universality (Multi-functionality)

4Stability of the object's composition

If full architectural serialization is applied to all MSR writes, then system consistency is maintained, but productivity and execution speed decrease

Engineering Contradiction:

Improvesystem consistencyVSAvoidexecution speed

Core Design Contradiction:

Stability of the object's compositionVSProductivity

Solution Approach 1:

The patent applies partial serialization through the WRMSRNS instruction, which provides just enough serialization to maintain system consistency for non-critical MSR writes without the excessive serialization overhead of the full WRMSR instruction. This partial action approach maintains the necessary system stability while dramatically improving execution speed for operations that do not require full architectural serialization.

Inventive Principle:

Principle #16Partial or excessive action

Data Source

PatentUS12572358B2System, apparatus and methods for minimum serialization in response to non-serializing register write instruction

Publication Date: 2026.03.10 INTEL CORP

AI summary

In one embodiment, a processor includes: a plurality of registers; a front end circuit to fetch and decode a non-serializing register write instruction, the non-serializing register write instruction to cause a value to be stored in a first register of the plurality of registers; and an execution circuit coupled to the front end circuit. The execution circuit, in response to the non-serializing register write instruction, is to determine an amount of serialization for the non-serializing register write instruction and execute the non-serializing register write instruction according to the amount of serialization. Other embodiments are described and claimed.