What happens with 4Gb RAM under XP?

[Agent]

Originally Posted by 306maxi

All the PAE switch lets you do is see the RAM. The OS will still only address 4gb of ram in total and will not use any additional RAM above this although you'll be able to see it.

Nope, it allows you to use the RAM / addressing space on a supported OS
Physical Address Extension - Wikipedia, the free encyclopedia

Originally Posted by dangel

PAE is a hack - go 64bit it's the only true way to use all the memory properly. Full Stop. Period. As in THATS YER LOT.

This has been discussed soooooooo much here.

Yup
Hack or not though, if it worked on XP32, most people would be happy enough with it. Although its just a waste having all these 64bit CPU's and not utilizing them. Its a shame XP64 wasn't more of a success.

[Paul Adams]

Still misconceptions abound...

Windows - 32-bit vs 64-bit

[dangel]

Well you can lead a horse to water..

[Thorsson]

Originally Posted by Paul Adams

Still misconceptions abound...

Windows - 32-bit vs 64-bit

Nice summary.

[JPreston]

Woo hoo, ~3.2 out of 4 is fine by me so 4Gb it is then. Cheers all

[2Cold Scorpio]

Originally Posted by JPreston

Woo hoo, ~3.2 out of 4 is fine by me so 4Gb it is then. Cheers all

Yeah, thats what I did (that, and getting 4GBs was only $20 more than what it would have gost me to get 2x1GB & 2x512MB sticks to get 3 GBs). lol Plus I know I'll go 64-bit bit eventually, so itsn ice already having the RAM.

[Baldrick2]

Hi

You guys could become all become heroes by offering a definative answer to this question!

Lets face it the Hexus forums are somewhere to go to get definative answers! And I apologise that this subject has arisen so many times.

Running AMD 64 X2 with XP Pro 32 bit, currently with 2GB RAM installed but have another 2GB sat here in a box waiting to go in.

Three questions really.

1. As, has been suggested in lots of other forums, will I suffer performance loss by installing the extra 2GB of RAM?

2. Which switch would be best to use. The /PAE or /3GB one in boot.ini. Should I use either, both or none?

I'm not bothered what sys info tells me I'm more bothered about performance and so am more concerned that not using a switch is going to affect it.

3. Should I change or 'disable' my page file?

There are litterally thousands of forum posts on tinternet about this, but no black and white answers. So I was over the moon when I found a thread on here, as you guys have helped me out in the past with your answers (browsing as an anonymous user).

Thanks in advance for the ultimate answer!

Balders

PS And I have absolutely no desire to move to a 64b OS at the mo and certainly never to Vista as I've seen it and had to use it, and don't like it.

[Agent]

1) In the 'real world' - No.
2) Neither, the /PAE switch is not used in XP-SP2 and the /3GB switch changes the way the kernel allocates memory to apps and itself and will make pretty much no difference IMO.
3) That depends on what you use your system for. I don't disable mine out of habit, but could probably get away with it. Also some programs have issues with installing / running without a pagefile.
The only changes I usually make to the pagefile are the size / set it to static.

[dangel]

Originally Posted by Agent

The only changes I usually make to the pagefile are the size / set it to static.

And that's all you should do. To disable the pagefile is to not understand how windows memory management works. The only time i've done it is on my EEE - and that's because i wanted to minimise flash writes. There is no good reason to do it otherwise - ever.

[Zak33]

the most important thing to note is that BUY RAM WHEN IT'S CHEAP

I have 4 gig on XP and 3.2 shows, but it's still better andf faster (especially when folding in the background on a quad) than 2 gig.

How do I know? I took 2 gig out....to see. Noticeable...so it went straight back in

[finnrogers]

Originally Posted by Zak33

How do I know? I took 2 gig out....to see. Noticeable...so it went straight back in

Awesome scientific observation!

[Baldrick2]

Thank you all very much, sorry I was delayed in replying (working!).

Threw the extra 2GB in the case, but then decided I should probably put it in the slots for maximum effectiveness (upped the voltage to it all as well)

Haven't done much else so haven't noticed any significant performance increase yet. As for disabling the page file I have seen it mentioned (other forums) as something to do in regards to this, but it just didn't seem right! I shall mess around with size settings at a later date. I currently have the page file spread across 4 of my 5 hdd's and noticed a massive improvement after I did this, but I'm thinking its probably far far too big now and will probably limit it to my OS drive cos I changed that to a Raptor (bloody noisy).

Thanks again for your help, it's really really appreciated.

Balders

[999tigger]

What Zak said.
It is way cheaper to buy 2gb on Scan than 3gb so it's a no brainer.

[Paul Adams]

Originally Posted by Agent

...the /PAE switch is not used in XP-SP2...

Actually, PAE is enabled by default in XP SP2, this is because DEP is turned on and requires PAE.
If you check the properties of My Computer you should see "Physical Address Extension" mentioned.

I set up a virtual machine in Hyper-V, gave it 1GB of RAM and installed XP SP2 to verify this - here is the kernel used according to the debugger:

lkd> lmvm nt
start end module name
804d7000 806cd280 nt
Loaded symbol image file: ntkrnlpa.exe

The "pa" bit indicates a PAE kernel.


I added a second boot option in BOOT.INI with "/noexecute=alwaysoff" and checked again - system properties no longer reads "Physical Address Extension" and the debugger shows a different kernel:

lkd> lmvm nt
start end module name
804d7000 806eb100 nt
Loaded symbol image file: ntoskrnl.exe

ntoskrnl = uni-processor, non-PAE kernel.


Next I added a 3rd boot option with "/noexecute=alwaysoff /pae" - back to "Physical Address Extension" visible on My Computer properties, and the debugger says:

lkd> lmvm nt
start end module name
804d7000 806cd280 nt
Loaded symbol image file: ntkrnlpa.exe


If it were a multi-processor kernel with PAE enabled, the nt module is ntkrpamp.exe ("pa" + "mp").