Newsgroups: comp.sys.ibm.pc.misc
Path: utzoo!censor!meadow!py
From: py@meadow.uucp (Peter Yeung)
Subject: Re: Memory Upgrades
Message-ID: <1990Oct30.193939.10607@meadow.uucp>
Keywords: memory
Reply-To: py@meadow.UUCP (Peter Yeung)
Organization: Amdahl Canada Ltd., Software Development Center
References: <272b5d9a.36d3@petunia.CalPoly.EDU>
Distribution: comp.sys.ibm.pc
Date: Tue, 30 Oct 90 19:39:39 GMT

In article <272b5d9a.36d3@petunia.CalPoly.EDU> ssenkere@polyslo.CalPoly.EDU (Scott Senkeresty) writes:
>
>understood the use of extra memory on your pc.  Other than the fact
>that some applications may require extra memory to run... what use
>is it?  Does it make your computer run any faster?  And, if you wanted
>

First, there are two types of "extra memory":

(1) EXPANDED memory (EMS or LIM) which is basically a memory switching
    scheme mapping memory pages into unused memory space; all PC's can use
    this type of memory (from 8088 to 486); on an 8088 based machine, you
    will need special EMS memory board and on 286/386/486 based machines,
    this is usually emulated by software utilizing EXTENDED memory (see
    below)

(2) EXTENDED memory is memory above 1Meg; you need a 286 or higher processor
    to handle extended memory; extended memory can only be addressed in
    protected mode
    
Many "heavy-weight" (read memory hog) commercial programs like Lotus 123 2.x
can utilize EMS to store data. While some can even put executables (e.g. TSR's)
in EMS (LIM 4.0 only).

There are only a few programs utilize extended memory. Usually those programs
switched into protected mode such that they can run in a much larger memory
space (in 286 protected mode you can address up to 16Meg). An example would
be Lotus 123 3.x. Another example of using extended memory is Windows 3 which
runs your regular real mode MS-DOS program in V86 mode (virtual 8086 mode).

Another very popular use of both EXPANDED and EXTENDED memory is for disk
cache. For example, in MS-DOS 4.x, there is a disk cache driver which can
utilize both type of memories.

>the extra memory to set up a ram disk, does this require any special
>hardware?   

If you are using an 8088/6 based machine, you will need an EMS board to
add the extra memory. If you have a more recently designed 286 (i.e >1Meg
on the motherboard) or a 386/486 machine, then all you need to add is the
extra memory (on the motherboard). If you have an older design 286 box
with only 1 Meg on the motherboard, you also need something like an Intel
Above board which can be configured into either EXPANDED or extended memory.

No, extra memory will not make your PROCESSOR runs faster per sec. However
it will enable your SYSTEM to run better (e.g. addition of disk cache, less
disk swapping under Windows). Just give you an example: I used to have
an XT clone with 1Meg of EMS, I configured it to have a disk cache of 768K;
when I was in an edit/compile cycle, subsequent compiles ran a lot faster
since most of the compiler/files were already in the disk cache.
-- 
Peter Yeung     Amdahl Canada Ltd., Software Development Center
                2000 Argentia Road, Plaza 2, Suite 300
                Mississauga, Ont.   L5N 1V8
                Phone: (416) 542-6300    Fax: (416) 858-2233