# 4gb RAM using 32bit XP ... can it be done?



## ian_heath

Hey all 

Seems I am seeing various opinions on whether or not 32bit version of windows (lets say XP Pro SP2) will run using all of a 4gb DDR2 upgrade.
Some threads all round state that it will only allow you to utilise 3gb.
Now I suspect they may be in fact referring to Vista, as even in Wiki's XP32 page it clearly states XP 32 bit will run up to 4gb RAM.

Can anyone confirm this?

And I also want to know if i plan on amping up my cpu (core2) clock should i perhaps opt for 800mhz RAM instead of the 1067mhz (pc8500) I currently use? What i mean is am i better off finding a lower rated ram with tighter CAS/CL timings??
I really want to improve the all round performance and if possible get my 3d card working to its full potential. (gaming)

I am considering "CORSAIR TWIN2X4096-6400C5" (system specs below)

Cheers

Ian


----------



## Done_Fishin

wrt Ram .. you can get to see 4GB of memory under 32bit but NOT UNDER XP.
Vista will run to 8GB
Motherboard specs will advise you how much RAM they support but unfortunately, depending upon what O/S you are using, you will either see it all or up to 3GB's. Some of the memory addressing conflicts (or could conflict if allowed to be useful) with addressing allocation for hardware or caches


----------



## blackduck30

Basically no normal 32bit operating system can use more than 3 to 3.5g of ram due to the 32bit address bus limitations. 
A 32bit address bus is limited to 4G, some of that is reserved for I/O devices ( usually 1G ) so this is what limits your system to see only 3 to 3.5G of ram. There has to be some bandwidth left for devices such as your video card, hard drives ect to use

32bit XP and vista have this limitation and it is only when you go to 64bit that you can overcome this


----------



## linderman

yeah I have seen win 32bit play ok with four gig / but definetely cant "use" the four gigs


and hordes of systems I have seen ran faster with 2 gigs compared to 3 gig and four gig configurations >>>>> the extra ram actaully slowed the system down in a major way :upset:


----------



## ian_heath

So now more memory "slows a system down"??

hmmm. personally i would take that comment to be pretty unsubstantiated and suspect that perhaps other factors (such as configs and system core components) may have played some part. 

In short, i am currently running only one of my HyperX pc8500 (2x512) kits and i can tell you 1gb is a faaarrrk load slower than my 2gb norm. In fact some games (such as Splinter Cell DA ) wont run (well) at all.
No matter how low i put 3d detail it just gives shocking refresh lags and is certainly unplayable. After some experimentation I have found that my system does not show great improvements when o/c the ram (perhaps as i chose the pc8500 which is 5-5-5-15) but some threads and tests i have read seem to confirm the same - usually efforts per result are best invested in the cpu rather than ram.

anyone disagree/clarify?

Ian


----------



## Kalim

2x1GB works best unless you're using major memory intensive applications and in that case go for x64. These applications are not games but professional software rather. 2GB is enough and best for gaming.

The volts you need for 4x1GB are higher and the latencies you can run with this amount of RAM installed are much higher than with 2x1GB. That's where the slowness comes from because the tRFC and other memeory timings have to be pretty slow.

I don't quite understand how you measured your system performance when overclocking RAM. You would need to test with memory intensive and dependent software to see the difference, i.e. compression/decompression, encoding/decoding, encryption/decryption, integer calculations, image rendering and so on. In either case the difference will not be massive like with more CPU MHz but still be noticeable if done right. To see an improvement of DDR2-800 over DDR2-1066 you will need to keep the latencies and sub-timings the same for both.


----------



## blackduck30

Ian,
I think you are confusing memory bandwidth and latency with how your system actually uses that.

Yes 2G is definitely faster than 1G as that still leaves 2G of bandwidth on your address bus for other I/O components to use, in some cases the more ram you add the less bandwidth there is for other I/O components.
There is only generally 1G reserved for these components so if you take your ram up to it's limit ( 3 to 3.5G ) and your I/O components require more than 1G then this can be detrimental to system performance

As far as your latency goes, if you are not running your ram at 1066 there is every chance you can manually tighten the timings to say 4-4-4-12

our reply's basically hinged around this statement



ian heath said:


> Seems I am seeing various opinions on whether or not 32bit version of windows (lets say XP Pro SP2) will run using all of a 4gb DDR2 upgrade.
> Some threads all round state that it will only allow you to utilize 3gb.


we are saying yes it will run with 4G of ram but no the system will not recognize all 4G basically due to the address bus also being 32bit ( 4G ) and part of that bus being reserved for things other than ram , your system will physically ignore some of that 4G of Ram. Saturating the address bus with ram can actually decrease performance.
64 Bit architecture overcomes this limit as everything has a larger allotment of bandwidth


----------



## speedster123

sort of like running a 454 engine with single exhaust..


----------



## linderman

are you of the opinion that three gigs will always run faster than 2 gigs ??


----------



## speedster123

not me, i just wanted to use an auto analogy. :laugh:


----------



## linderman

about 60% of the time you can get a cooperative motherboard that will run 2 x one gig sticks with a pair of 512's along side

but ram incompatabilites are very common with such a configuration

numerous times I have seen gamers add two gigs of ram to their existing two gigs only to find their FPS drop down to a ridiculous level

its really just a crap shoot, its worth the try if you are lucky to get the 3 gig set-up to run. Getting the bigger ram configs to run is easier than than get them to *run well*.


----------

