extended memory


Also found in: Dictionary, Medical, Legal, Financial, Wikipedia.

extended memory

(storage)
Memory above the first megabyte of address space in an IBM PC with an 80286 or later processor.

Extended memory is not directly available in real mode, only through EMS, UMB, XMS, or HMA; only applications executing in protected mode can use extended memory directly. In this case, the extended memory is provided by a supervising protected-mode operating system such as Microsoft Windows. The processor makes this memory available through a system of global descriptor tables and local descriptor tables. The memory is "protected" in the sense that memory assigned a local descriptor cannot be accessed by another program without causing a hardware trap. This prevents programs running in protected mode from interfering with each other's memory.

A protected-mode operating system such as Windows can also run real-mode programs and provide expanded memory to them. DOS Protected Mode Interface is Microsoft's prescribed method for an MS-DOS program to access extended memory under a multitasking environment.

Having extended memory does not necessarily mean that you have more than one megabyte of memory since the reserved memory area may be partially empty. In fact, if your 386 or higher uses extended memory as expanded memory then that part is not in excess of 1Mb.

See also conventional memory.

extended memory

The name given to memory (RAM) in an Intel PC above 1MB (one megabyte). Starting with the Intel 286, extended memory was used directly by Windows and OS/2 as well as DOS applications that ran with DOS extenders. It was also used under DOS for RAM disks and disk caches. Contrast with "expanded memory" (EMS), which was specialized memory above 1MB. Today, most people never heard of extended or expanded memory, because the 1MB barrier was broken long ago, and thousands of megabytes (MBs) of memory are commonly used. See EMS, XMS and DOS extender.


References in periodicals archive ?
The first Xeons with Intel's Extended Memory 64 Technology will be targeted at the workstation market.
The new products will support the latest Xeon processors and will feature support for a number of recent technologies such as PCI Express, DDR 2 and Intel Extended Memory 64 Technology.
Supermicro Computer's SuperServer platforms support Xeon processors with Intel Extended Memory 64 Technology (Intel EM64T).
The P800, announced in March this year, has built-in memory of 12Mb and with the extended memory could be used for file back-up and transfers between the phone and a PC, among other things.
DriveCam now offers full-color video playback, software-driven controls and an extended memory. The video-event recorder is part of a complete driving feedback system used by commercial fleets to monitor and improve driving performance.
The unit, an enhanced version of IDC's computerized M-1075 Leak Tester, also features extended memory. Housed in a compact unit 6.54 inches high, 12.63 inches wide, and 15.75 inches deep (160 x 320 x 400mm), it is easily incorporated into proprietary automated assembly/test systems.
This map is stored (or cached) in an area of extended memory. When an application asks for information on the disk, SMARTDrive intercepts the request and checks the map to see where the data resides.
Ideally, I would like to be able to plug something into my brain that would act as my extended memory. Obviously, we're not there yet, but who knows what will happen in the future.
System requirements for Janna Contact 95 are as follows: Microsoft Windows 95 operating system, a personal computer using an 80486DX/2 66Mhz or higher microprocessor, 640K of conventional memory and 16MB of extended memory, 8MB to 15MB of available hard disk space for programs plus approximately 1 MB for every 1,000 contacts.
It details features of DOS 6.22, such as DOS shell; better MemMaker; improved MEM command; new Del-Tree command; better use of extended memory; smarter SmartDrive; and Drive Space.
No matter how much extended memory a workstation carries, DOS applications are still constrained by the 640K conventional memory barrier.
There must be 150K of RAM available, or 512K without extended memory.

Full browser ?