Browse Definitions :
Definition

speculative execution

Speculative execution is an optimization technique in which a processor (CPU) performs a series of tasks before it is prompted to, in order to have the information ready if it is required at any point. Speculative execution uses concurrent processing and out-of-order execution (OoOE) to anticipate and fetch data that might be required at a latter point. It eliminates the stall experienced while waiting for appropriate instructions to arrive for the next step.  Speculative execution uses branch prediction to guess which instructions will most likely be needed in the near future and data flow analysis to arrange the instructions for optimal execution (instead of executing them in the order they came in). The goal is to reduce the total execution time and improve the overall CPU performance.

First, the branch predictor guesses which branch is most likely to be taken in the process and then gathers the next set of instructions associated with that branch. It will then begin speculatively executing them before it knows which of the two branches it will actually be using. If the branch predictor guessed correctly, then the instructions are already lined up and there will be no execution delay. If the branch predictor guessed incorrectly, then the system loads the appropriate information and proceeds with those instructions instead. However, accuracy rates for branch predictors are typically above 95 percent, so the need to reload new information is uncommon.

With in-order execution, a pipeline stall will stop the entire CPU until the issue is solved. Also, a gap is created between CPU and main memory speeds. As the gap grows, the time spent waiting for the main memory to deliver information to the CPU grows as well, thus increasing the time spent waiting on the execution. Speculative execution closes this gap by keeping the CPU busy and minimizing the time it spends idling, thus improving the overall performance of the system.

Speculative execution was adopted by Intel, who started using OoOE with its microprocessors Pentium Pro and Pentium II, Advanced Micro Devices (AMD), who introduced it with the K5 microprocessor, and Advanced RISC Machines (ARM), who began using it with the Cortex A9 microprocessor.

While speculative execution can improve the performance of a computer system, it is important to note that it may also cause security flaws such as meltdown CPU vulnerability.

This was last updated in June 2019

Continue Reading About speculative execution

Networking
  • voice over LTE (VoLTE)

    Voice over LTE (VoLTE) is a digital packet technology that uses 4G LTE networks to route voice traffic and transmit data.

  • ONOS (Open Network Operating System)

    Open Network Operating System (ONOS) is an OS designed to help network service providers build carrier-grade software-defined ...

  • telematics

    Telematics is a term that combines the words telecommunications and informatics to describe the use of communications and IT to ...

Security
  • three-factor authentication (3FA)

    Three-factor authentication (3FA) is the use of identity-confirming credentials from three separate categories of authentication ...

  • cyber espionage

    Cyber espionage (cyberespionage) is a type of cyber attack that malicious hackers carry out against a business or government ...

  • role-based access control (RBAC)

    Role-based access control (RBAC) is a method of restricting network access based on the roles of individual users within an ...

CIO
  • project charter

    A project charter is a formal short document that states a project exists and provides project managers with written authority to...

  • leadership

    Leadership is the ability of an individual or a group of people to influence and guide followers or members of an organization, ...

  • transaction

    In computing, a transaction is a set of related tasks treated as a single action.

HRSoftware
  • employee engagement

    Employee engagement is the emotional and professional connection an employee feels toward their organization, colleagues and work.

  • talent pool

    A talent pool is a database of job candidates who have the potential to meet an organization's immediate and long-term needs.

  • diversity, equity and inclusion (DEI)

    Diversity, equity and inclusion is a term used to describe policies and programs that promote the representation and ...

Customer Experience
  • sales development representative (SDR)

    A sales development representative (SDR) is an individual who focuses on prospecting, moving and qualifying leads through the ...

  • service level indicator

    A service level indicator (SLI) is a metric that indicates what measure of performance a customer is receiving at a given time.

  • customer data platform (CDP)

    A customer data platform (CDP) is a type of software application that provides a unified platform of customer information that ...

Close