I really need your help on this one!!! DOS!!

[Aurora]

Hi all..

Can any chaps or chapettes clear this up for me..?

I need to know the distinction in layman's terms between expanded and extended memory in DOS..

My thinking is that expanded is between 640k and 1024k (need emm386.exe in autoexec.bat), and that extended is everything above 1024K (need himem.sys in config.sys)..

I need to know this for a course that i am doing, and i am getting conflicting advice on the net and in books etc..

Your help would be really appreciated..

[Alan]

My memory is failing but I know they are not the same. If I remember, Extended was for 80286 processors and expanded was for 80386 processors with protected mode. They both referred to upper memory above 1Mb (remember RAM was the last 640k after BIOS, ROM, etc.
I think expanded could access higher memory than extended - it was certainly better for running big games.
And that's as far as I remember. I'll post back if the brain cells recover!
(P.S. some brainy plod who hasn't answered you yet will now quote chapter and verse to show up my inaccuracies - never fails) :D

[The Pimp]

Expanded Memory

Also known as EMS (Expanded Memory Specification), expanded memory is a technique for utilizing more than 1MB of main memory in DOS -based computers. The limit of 1MB is built into the DOS operating system. The upper 384K is reserved for special purposes, leaving just 640K of conventional memory for programs.
There are several versions of EMS. The original versions, called EMS 3.0 and 3.2, enable programs to use an additional 8MB of memory, but for data only. An improved version developed by AST, Quadram and Ashton-Tate is known as EEMS (Extended EMS). EEMS enables programs to use extra memory for code as well as for data. The most recent version of EMS (created in 1987) is known as EMS 4.0 or LIM 4.0, LIM being the initials of the three companies that developed the specification: Lotus, Intel, and Microsoft. EMS 4.0 raises the available amount of memory to 32MB.
Until the release of Microsoft Windows 3.0 in 1990, expanded memory was the preferred way to add memory to a PC. The alternative method, called extended memory, was less flexible and could be used only by special programs such as RAM disks. Windows 3.0 and all later versions of Windows, however, contain an extended memory manager that enables programs to use extended memory without interfering with one another. In addition, Windows can simulate expanded memory for those programs that need it (by using the EMM386.EXE driver).

Extended Memory


Memory above and beyond the standard 1MB (megabyte) of main memory (640Kb Base 384Kb Upper band) that DOS supports. Extended memory is only available in PCs with an Intel 80286 or later microprocessor.
Two types of memory can be added to a PC to increase memory beyond 1MB: expanded memory and extended memory. Expanded memory conforms to a published standard called EMS that enables DOS programs to take advantage of it. Extended memory, on the other hand, is not configured in any special manner and is therefore unavailable to most DOS programs. However, MS-Windows and OS/2 can use extended memory.

[Aurora]

Many thanks for your help guys.. It's appreciated