Mail Archives: opendos/2000/12/02/05:17:14
X-Comment-To: Patrick Moran
Hi!
1-δΕΛ-2000 03:57 pmoran22 AT yahoo DOT com (Patrick Moran) wrote to
<opendos AT delorie DOT com>:
PM> Okay, what the hello is XMS meory?
XMS is not a memory, but a specification, API to access extended
memory for "real mode" programs (see below).
PM> Is it ENTEDED meory or just another stupid swap em out memory?
XMS is not a memory, this is a specification how to exchange data
between conventional memory (for direct access) and extended memory (to
store data there).
PM> Extended memory does not swapping you are in
PM> memory above 1MB when you use ectended memory and you are in protected mode
PM> when using extended memory.
Please, don't mix extended memory itself and XMS API to access this
memory. When program work in "native" 386+ mode (so called "protected mode")
then it have full access to all physical/virtual memory and there is no
requirements to additional explicit APIs. But me talk not about "32bit"
programs (286 CPU is not 32-bit but this not change the idea), we compare
two specification to access additional memory (XMS and EMS) in "16bit"
programs which works in "real" mode (or in "V86" mode) and have "native"
access only to 1M of memory.
This thread started when you prosecute EMS as very bad specification in
compare with XMS. I try to show you: EMS have _only one_ contra - it cuts
frame for working from 1M addressing. This have nothing common with Windows,
Task manager, etc which are protected mode apps and don't require XMS and
EMS to access extended memory for itself.
PM> In Task manager, you are in protected mode and
PM> you use EXTENDED memory. There is no swapping of memory, each task is
PM> residing in a different area of memeory above 1MB and all you do when you
PM> swap windows or apps is to simply jump to that area of memory. Everything is
PM> running at the same time, it is multitasking, not the crap Gates came out
PM> with that merely swaps things around. Check out Linux sometime and see what
PM> is really, really TRUE MULITASKING.
This is _not_ "true" multitasking. True multitasking arise only on
multi-CPU systems, on one CPU you can have only time sharing system.
And which your hatting of "MS crap" have relation to XMS/EMS
"opposition"?
PM> DV is not a true multi-tasker, it shares CPU time between applications
PM> loaded, just like Gates' stupid WINDOZE does.
Wrong. Yes, Win 3.x is an "preemtive multasking" (i.e. cooperative
multitasking) but Win95 is an... hm, forget the word which describes
displaced multitasking... for Win95 native apps, also as DV, Linux and...
NT.
PM> When you use EXTENDED memory
PM> in protected mode, you actually run several processes simutaneously. In
When we use extended memory in protected mode, then this _not_ mean
"several process simultaneous running".
PM> virtual 86 mode you actually have each process running jst as though each
PM> one had it's own 8086 computer. It would be the same as running five tasks
PM> on five IBM XTs. or PCs.
PM> So what is XMS. And what does Task manager use.
Wrong - see above.
PM> I believe it uses DPMS which is DOS Protected Mode Services. That is
PM> what I use for multi-tasking in DOS.
PM> That is EXTENDED memory in PROTECTED MODE. I believe it is virtual 86
PM> protected mode that Task manager uses. There is no freeking memory swapping
PM> with Task manager.
PM> Desqview, on the other hand, uses stupid time consumming memory swapping
PM> through a tiny 64K window and uses stupid EMS to do it. Each process running
PM> is swapped into and out of conventional memory.
If this so then I think there was the real reasons (compatability, for
example) to do this.
PM> Task Manager DOES NOT do this.
PM> Don't get me wrong, I know that peole have an extremely hard time
PM> understanding the various memory areas and memory managers used and they can
PM> sit down with a comprehensive book about it and read the book half a dozen
PM> times and still not know what is going on with memory in the X86 line of
PM> CPUs. I never will figure out why IBM chose the X86 rather than the MC68000
PM> family or the Z8000 family or the MOS65000 family. They chose the worst
PM> possible CPU when they designed the PC after already having failed twice to
PM> enter the PC market. As you can clearly see IBM has a GREAT track record!!!!
I also not liked the Intel architecture (after DEC's PDP this look
freaky), but this have nothing with XMS/EMS opposition.
PM> I do not think we are talking about the same thing here. There is absolutely
PM> no swapping of memory with Task Manager. (except of course maybe some video
PM> memory on your video card and other such things.)
PM> But I would like to know just what XMS memory is. I thought it was extended
PM> memory, period. EXTENDED, PERIOD.
THIS IS NOT MEMORY. PERIOD. Both XMS and EMS are specification to
access additional memory. Simply on 386+ for EMS as additional used extended
memory.
PM> If it is not EXTENDED memory then we are
PM> deffinitely not talking about the same thing. I am talking about DPMS- DOS
PM> PROTECTED MEMORY SERVICE, which is used with Task Manager. There is no
PM> stupid memory swapping involved.
Again: protected mode programs don't require _any_ additional API for
access extended memory _for itself_.
PM> Try Linux sometime and you will not even mention things like EMS, XMS, DPMS,
PM> DPMI,VCPI and a ton of other crap.
Because Linux not based on real mode apps/system (i.e. DOS).
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