Increasing RAM has decreased PC performance

[The late XV105]

ASUS P5N32-SLI Premium motherboard with Intel Core Duo 2.4Ghz CPU.
Windows XP SP2 MCE 2005.
Maximum addressable memory with 32bit XP is 3.25GB.

I recently upgraded the above motherboard from 2x1GB 533Mhz DDR2 DIMMs to 4x1GB 667Mhz DDR2 DIMMs. All 4MB is detected by the BIOS and 3.25GB of it is addressed by XP. Great. :-)

Except not so great :-(

If I use up to .9GB memory, performance is fine
If I use between .9GB and 1.1 GB memory, performance tails off
If I use more than 1.1GB memory, the PC becomes slower than an asthmatic ant with some heavy shopping (to badly quote Captain Black Adder)

None of the memory sticks appear faulty because if I install 2GB by taking any two of the four DIMMs, performance is fine. It is only when I exceed 2GB that I have a problem.

My mobo handbook states that 667Mhz DDR2 is fully supported, as does the Crucial website.

I've written to Crucial for help, but would appreciate the wisdom of expert PPRuNers, please!


Cheers
XV105

[Forkandles]

Sounds like my machine. Increased the RAM from 2 to 4GB and has noticably slowed down while working.
Don't know if it's true on your system, but I upped the virtual memory in line with the increase in RAM and it seems to be using it a lot more than it was before. Could that be it? Continually swapping large files back and forward between the RAM and hard drive?

I'm using 3D CAD and it is slower now than when I had the previous version of the software and 1GB RAM. Go figure... :suspect:

[Guest 112233]

(i'm using 3.00 GB of DDRII - 2.8 or so addressable in XP) Things might be different if you re using XP Home - Like me and therefore you cannot address more than 1Gb in your user profile - If you have XP pro, maybe can you look at your user profile in settings, and allocate agreater cashe of RAM - also look at the system performance Tab in settings and try to maximise your program performance. Just an Idea. Does Win MCE XP
allow this


CATIII

[bucket_and_spade]

Could it be a mismatch in types/speeds of RAM? I hear that can sometimes cause slow working.

[The late XV105]

Nope. Four identical 667Mhz DIMMs from the same batch, from the same manufacturer.

[Jimmy Macintosh]

I'm with Bucket and Spade, I recently upgraded to 4 gig but I replaced all of the modules. Reading up on the memory it seems if the modules are mismatched in speed then the overall performance drops off significantly.

Are your modules the same PC rating? i.e PC2700, PC5400, PC6400 etc.?

To be honest I thought it was an immediate effect though rather than dependant on amount of usage.

Wasn't there a website PCpitstop or something that would run performance checks on your PC and make recommendations. It may (very remote chance) pick up on this issue.

***Took so long getting this thought out that you've already responded. :(

[The late XV105]

No probs, JM!

I have spent the last half an hour browsing the ASUSTEK website. It seems that me and everyone else with a P5N32 series mobo who tries to run 4GB has the same problem. There are countless posts describing precisely my problem, even down to symptoms such as music playback becoming j-i-t-t-e-r-y the same as I discovered mine does since last posting here.

I then had an idea; I know memory should be installed in balanced pairs but I can only address 3.25GB of my 4GB anyway so I wondered what would happen if I simply removed one DIMM leaving 3x1GB behind. The result?

BIOS detects 3GB :-)
XP addresses 3GB :-)
PC appears totally stable :-)
PC runs with its usual blazing performance whether I am hitting the RAM with just the .5GB or so footprint of XP or near maxed-out with 2.8GB during intensive video rendering :-)Video rendering was actually the reason I upgraded the RAM because large projects were slowed by swapping out to disk, so for the sake of "losing" .25GB of absolute ceiling, I'm happy.

[stickyb]

Windows XP will only run correctly on >3Gb if you
a) use XP Pro
b) use the /PAE and /3GB switches as required

See here for details.

A description of the 4 GB RAM Tuning feature and the Physical Address Extension parameter (http://support.microsoft.com/kb/291988)

[stickyb]

Sounds like my machine. Increased the RAM from 2 to 4GB and has noticably slowed down while working.
Don't know if it's true on your system, but I upped the virtual memory in line with the increase in RAM and it seems to be using it a lot more than it was before. Could that be it? Continually swapping large files back and forward between the RAM and hard drive?

I'm using 3D CAD and it is slower now than when I had the previous version of the software and 1GB RAM. Go figure... :suspect:

Quite logical under some conditions.

The memory is normally split 50/50 between kernel and user, so on a 2 Gb system only 1Gb of user memory would need swapping. Go to a 4Gb system and user space is now 2Gb, more to swap.

If, and only if, your CAD application can support a 3Gb address space then switch Windows to use 3Gb user space and 1Gb system space and it should be much faster.

[The late XV105]

Thanks, stickyb.

I'm happy now that I have 3GB RAM working properly since it is adequate for my needs (my most extreme usage typically peaks at about 2.8GB) and I only upgraded from 2GB to 4GB since I wanted to install balanced pairs (4x1GB).

The linked article you kindly posted is however very interesting and in turn it links to an excellent series of Blogs on memory management. :)


Cheers,
XV105