Browse Definitions :
Definition

extended memory

Extended memory, also known as XMS (eXtended Memory Specification) is a technology that enables capacity above the 640KB standard MS-DOS limit of main memory.

Extended memory was introduced in the Intel 80286 processor, increasing the amount of addressable memory beyond what was introduced in the similarly named expanded memory (EMS). Prior to XMS, expanded memory was used to increase the 640KB upper limit of DOS to 1MB using a gated memory card riser.

Extended memory initially boosted the addressable memory to 16MB. XMS 2.0 extended the capacity to 64GB and XMS 3.0 to up to 4GB. Beyond XMS 3.0, AMD64, the de facto x86-64 standard, expands maximum memory to 256TB.

Programs written to use expanded memory would be redirected by driver emulation to use extended memory’s upper memory area instead. This process involved no special hardware, just increased RAM and support in the processor design.

Extended memory can only be addressed by software running in protected mode as all but the small portion of upper memory are unreadable by programs running in standard real mode.

Fun fact: The 640KB upper limit of DOS is the alleged source of the often-quoted but steadfastly denied Bill Gates statement: “640KB ought to be enough for anyone.”

This was last updated in February 2014
SearchNetworking
SearchSecurity
  • Patch Tuesday

    Patch Tuesday is the unofficial name of Microsoft's monthly scheduled release of security fixes for the Windows operating system ...

  • parameter tampering

    Parameter tampering is a type of web-based cyber attack in which certain parameters in a URL are changed without a user's ...

  • SYN flood attack

    A SYN flood attack is a type of denial-of-service (DoS) attack on a computer server.

SearchCIO
  • Lean Six Sigma

    Lean Six Sigma is a data-driven approach to improving efficiency, customer satisfaction and profits.

  • change management

    Change management is a systematic approach to dealing with the transition or transformation of an organization's goals, processes...

  • business transformation

    Business transformation is a term used to describe what happens when a company makes fundamental changes to how it operates.

SearchHRSoftware
SearchCustomerExperience
  • clickstream data (clickstream analytics)

    Clickstream data and clickstream analytics are the processes involved in collecting, analyzing and reporting aggregate data about...

  • neuromarketing

    Neuromarketing is the study of how people's brains respond to advertising and other brand-related messages by scientifically ...

  • contextual marketing

    Contextual marketing is an online marketing strategy model in which people are served with targeted advertising based on their ...

Close