4GB in windows xp pro

[CTS]

I know this question has been overdone and covered quite a bit so i must
apologize. I have an xp pro machine a gigabyte GA-8IPE1000L motherboard and a
3.2G P4 with hyperthreading. I already have 2GB and I'm about to get 2 more
GB of memory same exact type that I have in there. I've read quite a bit
about the 3GB switch and the PAE switch in the boot.ini but what I wanted to
know is that know matter what it sees or shows whehter its 3GB or 3.5Gb.all I
want is the best performance possible from my machine. Do i have to use those
switches or does it work much better if i put in the memory and not add any
switches. Also are there any more "tweaks" to make the most of what i'm
getting.

 

[Colin Barnhorst]

The amount of memory available to user programs varies from 2.5 to 3.5
depending on the devices and the BIOS. x86 Windows can address 4GB but the
BIOS will reserve some for hardware buffering (memory-mapped IO). You don't
need PAE. You can make some adjustments in the BIOS for the memory mapped
IO but I wouldn't bother. Even if 4GB was reported on the system properties
page like it now is in Vista x86 SP1 the amount available to user programs
would not change since it is only a matter of what is being reported.

 

[jorgen]

I've read quite a bit
about the 3GB switch and the PAE switch in the boot.ini

With proper hardware support, PAE is normally the way to go in 32-bit
OSes. But the PAE kernel in XP/SP2 doesn't allow more than 4GB to be
addressed in total, so when it comes to memory support, it doesn't
matter if you enable PAE or not.

Google DEP, if you want to know why there is a PAE kernel

 

[CTS]

Thank you both for the quick reply. It sounds as if i should leave it
settings alone and see what that does for my machine. I have yet another
(probably stupid) question, My motherboard supports dual channel DDR, If all
four sticks are matched then even if all the memory doesn't show, will
whatever does show run in dual channel mode?

 

[Thee Chicago Wolf]

Thank you both for the quick reply. It sounds as if i should leave it

settings alone and see what that does for my machine. I have yet another
(probably stupid) question, My motherboard supports dual channel DDR, If all
four sticks are matched then even if all the memory doesn't show, will
whatever does show run in dual channel mode?

You could always try both PAE and none and see if either one has any
benefit one your particular setup and let the group know how it went.
We'd all be interested to hear your results.

- Thee Chicago Wolf

 

[Colin Barnhorst]

Yes. The same amount of memory shows regardless of the mode.

PAE is normally not useful on XP with only 4GB of ram. It is not designed
to resolve the issue you are addressing. Here is an article on PAE:
http://msdn2.microsoft.com/en-us/library/ms791485.aspx
As you can see PAE addresses specific needs involving NUMA and DEP and is
automatically enabled or disabled as required. The needs concern certain
driver bugs. Even with PAE switched in you won't see 4GB but would see
slightly different numbers from what you do now. See:
http://support.microsoft.com/?kbid&ID=888137

I doubt that you can twiddle enough in the BIOS to recover any significant
ram for user programs. Remember, there are two of you using the computer;
you and the computer.

 

[jorgen]

PAE is normally not useful on XP with only 4GB of ram. It is not
designed to resolve the issue you are addressing. Here is an article on

It is true that it is not useful on XP, because Microsoft has limited
it. But Intel actually invented PAE to address more than 4GB, and that
is exactly was is needed here to make use of all the 4GB RAM

 

[Colin Barnhorst]

Yes, it is for addressing more than 4GB of ram. Not for using all of 4GB
but for accessing the addresses above 4GB that are not normally addressable
with a 32bit OS. It is also used to circumvent certain driver bugs.

 

[CTS]

At this point I don't think i'm going to mess with PAE or 3GB switches. I
just want to know that whatever memory windows or my apps can use will still
make use of the dual channel and hyperthreading capabilities. I want it all
to run the best that it can

 

[Colin Barnhorst]

You are good to go. The memory controller handles everything and the mode
is transparent to your apps. Hyperthreading is not really a matter of
memory modes. That is handled by the scheduler.

 

[jorgen]

Yes, it is for addressing more than 4GB of ram. Not for using all of
4GB but for accessing the addresses above 4GB that are not normally
addressable with a 32bit OS. It is also used to circumvent certain
driver bugs.

Most new computers have a memory remap feature, when activated it will
remap some of your ram, so it doesn't collide with your mmio space. If
Microsoft allowed more than 4GB to be addressed, you could then have all
4GB RAM available to you

 

[Tim Slattery]

Yes, it is for addressing more than 4GB of ram. Not for using all of 4GB
but for accessing the addresses above 4GB that are not normally addressable
with a 32bit OS.

And being able to use those higher addresses would allow use of the
entire 4GB of RAM. After allocating addresses for the BIOS, video
memory and other things there would be more than enough addresses
remaining to access all 4GB of system RAM.

But since that's not what Microsoft implemented, the subject is moot.

 

[Tim Slattery]

At this point I don't think i'm going to mess with PAE or 3GB switches.

IMHO, that's the right decision.

 

[Ken Blake, MVP]

I know this question has been overdone and covered quite a bit so i must
apologize. I have an xp pro machine a gigabyte GA-8IPE1000L motherboard and a
3.2G P4 with hyperthreading. I already have 2GB and I'm about to get 2 more
GB of memory

In addition to the answers you've already, why are you about to get
more RAM?

Unless you run particularly memory-hungry applications, 2GB of RAM
under Windows XP is already overkill for most people. My guess is that
adding any more RAM will make no performance difference to you at all.
Despite the many people who continually repeat "the more memory the
better," that's true only up to a point. For most people that point is
somewhere between 256-512MB, and except for those doing something like
editing videos or large photographic images, is almost always no
greater than 1GB.

 

[Colin Barnhorst]

Virtual machines are also memory hungry.

In addition to the answers you've already, why are you about to get
more RAM?

Unless you run particularly memory-hungry applications, 2GB of RAM
under Windows XP is already overkill for most people. My guess is that
adding any more RAM will make no performance difference to you at all.
Despite the many people who continually repeat "the more memory the
better," that's true only up to a point. For most people that point is
somewhere between 256-512MB, and except for those doing something like
editing videos or large photographic images, is almost always no
greater than 1GB.

 

[Ian D]

Most new computers have a memory remap feature, when activated it will
remap some of your ram, so it doesn't collide with your mmio space. If
Microsoft allowed more than 4GB to be addressed, you could then have all
4GB RAM available to you

That's only for 64 bit OSs. If you do the BIOS memory remap feature
with 32 bit XP, you're likely to lose a GB, ie., from 3.xx GB to 2.xx GB
reported in Task Manager.

 

[Ken Blake, MVP]

Virtual machines are also memory hungry.

Yes, certainly. I meant "editing videos or large photographic images"
only as examples, not as an exhaustive list.

 

[jorgen]

That's only for 64 bit OSs. If you do the BIOS memory remap feature
with 32 bit XP, you're likely to lose a GB, ie., from 3.xx GB to 2.xx GB
reported in Task Manager.

Yes, that is why we say that XP cannot take advantage of it, because
Microsoft has crippled the pae kernel, it they didn't ... you could,
just like you can in their server editions and in Linux

 

[John Ringoes XIII]

NOW YOU TELL ME!

I was wondering why taskmanager rarely rose above 400 mb. So does this mean
I need an in-memory virtual hard drive emulation utility like we had in the
bad old DOS days in order to utilize all that memory?

John

 

[Ken Blake, MVP]

NOW YOU TELL ME!

I was wondering why taskmanager rarely rose above 400 mb. So does this mean
I need an in-memory virtual hard drive emulation utility like we had in the
bad old DOS days in order to utilize all that memory?

I don't know what you mean by "an in-memory virtual hard drive
emulation utility," but if you don't run apps that need that much
memory, there's nothing you can do to effectively use it.