XP and Memory Usage.....

  • Thread starter Thread starter darin m
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darin m

Does anyone know how the XP system uses memory. I.E. Does
the OS use the memory like the previous versions?
50% of the RAM for Applications and 50% for the OS?
so if the machine has 1 GB RAM does that mean it only has
512 usable before it goes to virtual mem?
I am trying to find a way to increase the split between
the Apps / OS like 75-25 or something. Similar to
the /3GB switch in WIN2K.

any information would be helpful.

THanks.
 
XP supports the /3GB switch, and the memory management is
much the same as Windows 2000, but you seem to be
slightly confused on what it actually does.

Each process (application) has access to a 4 GB virtual
memory address space. Obviously since you'll have 20+
processes running at any time, and no home machine has 80
GB of RAM, some translation has to be done.

Under normal conditions, the process can actively access
2 GB of this 4 GB space. The other 2 GB is set aside for
OS files that are loaded and/or drivers that need to be
loaded in that space.

So, each application can allocate up to 2 GB of virtual
RAM space, all else being equal. If the machine doesn't
have enough physical RAM to satisfy every application's
requests, the OS memory manager determines (with help
from the application) what can be swapped out to disk,
and what needs to stay in physical RAM.

With the /3GB switch turned on, the OS allows the
application to allocate up to 3 GB of virtual RAM space,
leaving the remaining 1 GB in its space for the OS and
drivers.
You will only see a noticable performance benefit if the
application needs that extra space (and understands how
to access it), and you have the physical RAM to handle it.

90% (or more) of applications will see no benefit at all
to turning /3GB on, and depending on the system, you may
experience problems with it on.

In your statement about if the machine has 1 GB of RAM,
the OS will attempt to use all that it can, there is no
50-50 split-type thing.
 
darin m said:
Does anyone know how the XP system uses memory. I.E. Does
the OS use the memory like the previous versions?
50% of the RAM for Applications and 50% for the OS?
so if the machine has 1 GB RAM does that mean it only has
512 usable before it goes to virtual mem?
I am trying to find a way to increase the split between
the Apps / OS like 75-25 or something. Similar to
the /3GB switch in WIN2K.

any information would be helpful.

THanks.
Click to expand...

There is no way to control the allocation of physical RAM between the
operating system and application programs with anything less than 2 gb
of RAM.

You seem to be confusing allocation of the virtual address space (the
total 4 gb that is addressable by the CPU. That theoretical space is
allocated into segments for application programs and for the operating
system.

However translation of these virtual addresses into physical locations
in RAM is controlled by the Windows memory manager and in that
translantion the rule is "what you need is what you get". So if the
application load is such that the actual RAM requirements equal 70
percent of they physical RAM then that is what the applications will
get, subject to availability and priorities.


Ron Martell Duncan B.C. Canada
--
Microsoft MVP
On-Line Help Computer Service
http://onlinehelp.bc.ca

"The reason computer chips are so small is computers don't eat much."
 
darin said:
Does anyone know how the XP system uses memory. I.E. Does
the OS use the memory like the previous versions?
50% of the RAM for Applications and 50% for the OS?
Click to expand...

No it doesn't. And I am not at all sure that *any* version of windows
ever did just that. Read up at www.aumha.org/win5/a/xpvm.htm
 
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