User Guide

  • 2020
  • 06/18/2020
  • Public Content

MS Assists

Metric Description

Certain corner-case operations cannot be handled natively by the execution pipeline and must be performed by the microcode sequencer (MS), where 1 or more uOps are issued. The microcode sequencer performs microcode assists (small programs injected into the execution stream), inserting flows, and writing to the instruction queue (IQ). For example, when working with very small floating point values (so-called denormals), the floating-point units are not set up to perform these operations natively. Instead, a sequence of instructions to perform the computation on the denormal is injected into the pipeline. Since these microcode sequences might be hundreds of instructions long, these microcode assists are extremely deleterious to performance.

Possible Issues

A significant portion of execution time is spent in microcode assists, inserted flows, and writing to the instruction queue (IQ). Examine the FP Assist and SIMD Assist metrics to determine the specific cause.

Product and Performance Information


Intel's compilers may or may not optimize to the same degree for non-Intel microprocessors for optimizations that are not unique to Intel microprocessors. These optimizations include SSE2, SSE3, and SSSE3 instruction sets and other optimizations. Intel does not guarantee the availability, functionality, or effectiveness of any optimization on microprocessors not manufactured by Intel. Microprocessor-dependent optimizations in this product are intended for use with Intel microprocessors. Certain optimizations not specific to Intel microarchitecture are reserved for Intel microprocessors. Please refer to the applicable product User and Reference Guides for more information regarding the specific instruction sets covered by this notice.

Notice revision #20110804