Vista 32-Bit 2GB vs. 3GB

[Rob Williams]

I did a few tests the other day and will share the findings here for anyone who is interested. Basically, since Vista 32-Bit only allows up to 3GB of ram, I wanted to test the differences between 2GB and 3GB with various scenarios.

2 x 1GB
5657MB/s - 5608MB/s (58.3ns Latency)

3 x 1GB
5154MB/s - 5149MB/s (56.1ns Latency)

4 x 1GB (Note at -no- time would all 4GB be accessed)
5653MB/s - 5652MB/s (59.4ns Latency)

2 x 1GB + 2 x 512MB
5672MB/s - 5682MB/s (59.1ns Latency)

2 x 1GB DDR2-800 1T
5632MB/s - 5678MB/s (55.4ns Latency)

The thing to note, is that with 3GB or more of ram, my particular motherboard would only allow Windows to see 2.75GB. Yours will be different (unless you have the same motherboard) which would effect the bandwidth and latency results more. Overall though, it should all scale relatively close regardless of boards.

http://deathspawner.net/etcetera/pictures/forum_posts/vista/4gb/2x1_thumb.jpg (http://deathspawner.net/etcetera/pictures/forum_posts/vista/4gb/2x1.jpg) http://deathspawner.net/etcetera/pictures/forum_posts/vista/4gb/3x1_thumb.jpg (http://deathspawner.net/etcetera/pictures/forum_posts/vista/4gb/3x1.jpg)

http://deathspawner.net/etcetera/pictures/forum_posts/vista/4gb/4x1_thumb.jpg (http://deathspawner.net/etcetera/pictures/forum_posts/vista/4gb/4x1.jpg) http://deathspawner.net/etcetera/pictures/forum_posts/vista/4gb/2x1x512x2_thumb.jpg (http://deathspawner.net/etcetera/pictures/forum_posts/vista/4gb/2x1x512x2.jpg)

http://deathspawner.net/etcetera/pictures/forum_posts/vista/4gb/2x1-1T_thumb.jpg (http://deathspawner.net/etcetera/pictures/forum_posts/vista/4gb/2x1-1T.jpg)

The conclusion? If you want 3GB, you will likely want 3 x 1GB for better overall latency. If higher bandwidth is your concern, going with 2 x 1GB + 2 x 512MB will be the better method.

Really though, I would not go with 3GB on purpose, unless you already have a bunch of sticks lying around. If you want to go above 2GB you may as well just get the 64-Bit version of Vista and use 2 x 2GB or 4 x 1GB for the best overall solution.

[MakubeX]

What?! Every version of Vista 32-bit allows only up to 3GB?! Well that sucks! Yet another reason not upgrade to Vista yet.

I wouldn't even get Windows XP 64-bit yet, let alone Vista 64-bit.

[Rob Williams]

It's a limitation of the 64-Bit architecture in general, not just with Windows. I know a few people who have been using the 64-Bit version day in and day out and have experienced a lot of problems, but I think they are the same issues found in the 32-Bit as well.

I did have a few people e-mail me regarding lack of drivers for their hardware in 64-Bit though. 64-Bit is for those who actually need more than 3GB of ram... aside from that I'd say the 32-Bit by far makes more sense.

[madstork91]

I'll stop using my 32bit os when they pry it from my systems smooth running daily operations in need for something more graphic and processing intensive. Till then, im only intrigued by threads like this.

[MakubeX]

I completely agree, the software world is still not ready for 64-bit. It's not that the technology is not available, is just that right now almost everything is optimized for 32-bit. Switching to 64-bit right now can just lead to more problems, like incompatible or unstable drivers (being one of the most common problems).

But it does sucks to know that Windows Vista 32-bit is capped at 3GB. Instead of moving forward, it's going backwards. Hardware is supporting more memory everyday and yet software is holding it back.

[Rob Williams]

" But it does sucks to know that Windows Vista 32-bit is capped at 3GB. "

Remember that's out of Microsofts control, because it's an arch issue, not their issue. 4GB doesn't work with 32-Bit Linux, either.

On the other side of the coin, they could not have just released 64-Bit versions for two reasons. Many people still don't have capable computers, and there are still too many problems. Vista has enough problems as is, don't need a 64-Bit version ;-)

[MakubeX]

But how does Windows XP 32-bit handle 4GB?

[Rob Williams]

Windows XP 32-Bit doesn't handle 4GB, it will only recognize 2.75 - 3.15GB of it.

[MakubeX]

Ooohhhh, I thought XP could handle 4GB or maybe more. That's why I was so disappointed that Vista 32-bit could only handle 3GB.

Funny how motherboard manufacturers keep increasing memory capacity for their mobos when the software can barely handle today's needs.

[Rob Williams]

Well, if you have a 64-Bit OS you can use a lot more memory ;-)

They just give people the ability, if they want it. No harm in that.

[MakubeX]

How much more? Wasn't 4GB the max 64-bit OS can handle?

[Rob Williams]

Ok, bear with me. 32-Bit is meant to register 2^32 addresses, which is 4,294,967,296 (4GB). 64-Bit however registers 2^64, or 18,446,744,073,709,551,616 (18,446,744,073GB, 18EB).

So we have a lot of breathing room here.

[MakubeX]

I see, so in theory 32-bit can handle 4GB, it's just M$ that couldn't make their software do it, or even close. Is that about right?

This means that their 64-bit software is even farther (MUCH farther) away from tapping into 64-bit's real potential.

[Rob Williams]

Essentially, yes. Even though 2^32 can support 4GB, it might not access ALL of it at once. In 32-Bit, it CAN use all 4GB, but only 3GB of it at any given time, if that makes sense. Your computer will see 4GB, but won't be able to use all of it at once.. that's the only way I can explain it, hehe.

As for whether it's a simple Windows problem or not, I'm not sure. If I can find time over the next week, I will install Linux on that rig and install 4GB of ram and try to run a few applications that will stress as much ram as possible. Linux is a little different though, since it relies a lot on Swap space as well. I will see though...

"This means that their 64-bit software is even farther (MUCH farther) away from tapping into 64-bit's real potential."

Oh for sure. As far as I know, even if you added together all the hard drives in the world, you would not hit 18 Exabytes, let alone that much ram in a single computer. With 64-Bit OS', memory is not the issue anymore. Even with 64GB of ram in a single computer, it wouldn't do much good for a normal rig... there are many other bottlenecks. You probably wouldn't be able to use enough CPU operations in order to use that much ram at once, for example.

So in the future with 128-Bit CPUs, it wouldn't be an increase in order to add more memory... it would be to add other capabilities. We are still trying to find uses for 64-Bit, so 128-Bit won't be for quite a long while.

[MakubeX]

I see what you mean.

Just as an FYI, I'm not trying to flame M$ for not being able to use all 4GB (or close to) at the same time in their OS. I'm just using them as an example to say that even though 32-bit is capable (at least in theory) of handling 4GB, it's the software that isn't there yet.

In practice, it may not even be possible to make it handle the whole 4GB at the same time, but I bet it can come pretty close. At least much closer than what Windows XP or Vista can today.

Don't worry about the Linux thing, I know you're probably very busy. That is unless you really wanna do it. :p

Thanks again Rob.

[Rob Williams]

Hah, well actually now that I think of it... I don't think I need to do Linux testing. I am not sure why, but sometimes things just "come" to me.

4GB was possible for WinXP back in the day, but SP2 took the ability to use it out, for whatever reason. I believe it was something to do with some security feature, but it really, really made no sense to me.

So, 4GB is possible with 32-Bit OS, including Linux. No idea why I thought otherwise there.

[MakubeX]

Good to know. Can't wait to see what they'll do with 64-bit. :D

[Rob Williams]

I just ordered a kit of 18 Exabyte ram for only $1.575 trillion dollars. I will let you know how that goes ;-)

[MakubeX]

I just ordered a kit of 18 Exabyte ram for only $1.575 trillion dollars. I will let you know how that goes ;-)
LoL, can't wait for some benchmarks. :p

[Deth]

Hello :)

Glad I found this post. I recently bought a new computer

(EVGA nForce 680i // EVGA GeForce 8800GTX 768MB KO // C2D E6600 @ 3.6GHz, 1.4875V // Thermalright SI-128 // CORSAIR XMS2 2GB DDR2 800 // Thermaltake Toughpower 850W // 2x WD Raptors 150GB in RAID 0 // 3ware 9500S-4LP // Creative SB X-Fi XtremeGamer // NZXT Zero Full Tower)

and I've been reading various articles concerning the memory limit on Windows Vista 32-bit the entire day. After reading my 70th article, I came across two that were very interesting to me. One written by Rob Williams,

2 x 1GB
5657MB/s - 5608MB/s (58.3ns Latency)

3 x 1GB
5154MB/s - 5149MB/s (56.1ns Latency)

4 x 1GB (Note at -no- time would all 4GB be accessed)
5653MB/s - 5652MB/s (59.4ns Latency)

2 x 1GB + 2 x 512MB
5672MB/s - 5682MB/s (59.1ns Latency)

2 x 1GB DDR2-800 1T
5632MB/s - 5678MB/s (55.4ns Latency)


and the other by Microsoft.

http://support.microsoft.com/kb/929580

My question is, if I installed another 2GB of CORSAIR XMS2 2GB DDR2 800 and followed the instructions by Microsoft (enable PAE mode so the OS recognizes the 4GB of physical RAM), would there be any overall performance decrease? ie. would my latency or bandwidth decrease compared to what I already have now?

Can any of you test this and reply back please? If this works out, this would be a good reason for me to upgrade to 4GB of ram, enable PAE mode, and keep my current Vista 32-bit OS (saves me money) + 32-bit drivers rock.

[MacMan]

I see what you mean.

Just as an FYI, I'm not trying to flame M$ for not being able to use all 4GB (or close to) at the same time in their OS. I'm just using them as an example to say that even though 32-bit is capable (at least in theory) of handling 4GB, it's the software that isn't there yet.

In practice, it may not even be possible to make it handle the whole 4GB at the same time, but I bet it can come pretty close. At least much closer than what Windows XP or Vista can today.

Don't worry about the Linux thing, I know you're probably very busy. That is unless you really wanna do it. :p

Thanks again Rob.

Duh! That's strange. You would think that a super-gigantic corporation like Microsoft could build an OS that was completely 64-bit, but yet, at-the-same-time, capable of running any and all 32-bit programs natively, at full-speed, with out any kind of performance hit? Why two separate OS's, 32 and 64-bit? Why not just the one that handled both in one shot, with full-performance?

Seems rather simple to me. Seriously, how hard can it be? Is it technically impossible as I was told by some Window's technies once? Personally, I know that is not the case. The reason I say that is simply because I have already seen an OS demoed doing just that, one system running both 32-bit and 64-bit simultaneously, and both running at maximum speed, etc.


http://www.apple.com/macosx/leopard/64bit.html

I rest my case. :)

[Rob Williams]

My question is, if I installed another 2GB of CORSAIR XMS2 2GB DDR2 800 and followed the instructions by Microsoft (enable PAE mode so the OS recognizes the 4GB of physical RAM), would there be any overall performance decrease? ie. would my latency or bandwidth decrease compared to what I already have now?

Hi Deth,

I have never had luck with /PAE in the past, but I will give it a go in Vista tomorrow (Friday) and let you know the results of my quick testing. Technically, the results should be near identical to the result here:

4 x 1GB (Note at -no- time would all 4GB be accessed)
5653MB/s - 5652MB/s (59.4ns Latency)

Because of the wider bandwidth, there will likely be a very small latency hike (0.4% - 0.7%) and also an even more minor MB/s drop. I'll test these out tomorrow quickly in both 32-Bit and 64-Bit Vista and see if that proves true.

[Rob Williams]

Duh! That's strange. You would think that a super-gigantic corporation like Microsoft could build an OS that was completely 64-bit, but yet, at-the-same-time, capable of running any and all 32-bit programs natively, at full-speed, with out any kind of performance hit? Why two separate OS's, 32 and 64-bit? Why not just the one that handled both in one shot, with full-performance?

Seems rather simple to me. Seriously, how hard can it be? Is it technically impossible as I was told by some Window's technies once? Personally, I know that is not the case. The reason I say that is simply because I have already seen an OS demoed doing just that, one system running both 32-bit and 64-bit simultaneously, and both running at maximum speed, etc.

http://www.apple.com/macosx/leopard/64bit.html

I rest my case. :)

Windows has a poor base, that's why it won't run all 32-Bit applications perfectly under a 64-Bit environment. I haven't done in-depth testing, so I can't elaborate. My experiences under any x64 OS have been less than stellar.

As for Leopard, I still would like to see 32-bit vs 64-bit benchmarks to see how much of a benefit there would be with the latter. Sure it's a 64-Bit environment, but -how- does that benefit anyone? I've run countless benchmarks and have more often seen decreases under 64-Bit than 32-Bit.

I might test it out tomorrow with 3DS Max w/ 4GB of ram and under 32-Bit and 64-Bit Windows and report the findings here at the same time as the other testing mentioned above. You've got me curious :-)

[Deth]

Rob Williams: Do you recommend I go 4 x 1GB or 2 x 1GB + 2 x 512MB? I really want to stick with Windows Vista 32-bit because of the driver problems with 64-bit. I'm not sure if /PAE would solve my problem because so far it seems no one has had any success with it to my knowledge.

I have no performance issues currently whatsoever so I'm wondering if I should even get another gig or two of RAM?

If /PAE works for me, I would much rather get another 2 x 1GB.
If I would ever choose to upgrade to 64-bit Vista later (unlikely), 2 x 1GB would also be the better choice.

If Vista 32-bit won't recognize my 4GB of physical RAM, then going with 2 x 1GB + 2 x 512MB set up would be better economically and save me $100 that would otherwise be wasted.

But how much of a difference can 1GB make if I'm experience no problems and everything is on the highest quality settings and there are no performance issues, everything is smooth.

I think the only reason I want to upgrade is because I'm crazy about more "performance" when in essence I may not notice any. Lol. What should I do?

[Cjmovie]

There is no architectural limitation that forces use of 3GB, or even 4GB, of RAM in a 32-bit operating system. Sure, a 32-bit mode of a 64/32 bit processor can only access 4GB at a time. Of this, windows usually uses the top 1GB of space, regardless of how much "actual" RAM it uses. It's called virtual memory. It can map any address within that 4GB to any point in physical RAM, and it has a different mapping for every application (but not thread; this is how it keeps processes safe from each other, and is very common. There are very few OS's not using it, and these most likely use a segmented architecture, like AmigaOS).
Now, there was an addition quite a while ago (Pentium Pro architecture?) that extended the _external_ bus of the processor, called PAE, or physical address extension. This allows RAM of amounts past 4GB (such as 16GB. It varies on implementation) to be accessed by "mapping" it to a range within 4GB, and changing it out for each program. Each individual application is still limited to 3GB (4GB = 3GB for application + 1GB for Windows mapping).

Read up on it:
http://en.wikipedia.org/wiki/Physical_Address_Extension
http://en.wikipedia.org/wiki/Page_table

Or, if you're really daring, do what I did: Order and read the Intel Architecture Developer's manuals. They're free, shipping and everything.

[Deth]

Thanks. Think I read enough today. I'm thinking about getting:

CORSAIR XMS2 1GB (2 x 512MB) 240-Pin DDR2 SDRAM DDR2 800 (PC2 6400) Dual Channel Kit Desktop Memory


to add to my:

CORSAIR XMS2 2GB (2 x 1GB) 240-Pin DDR2 SDRAM DDR2 800 (PC2 6400) Dual Channel Kit Desktop Memory Model TWIN2X2048-6400C4


If that sounds like a good idea (or not), let me know!

Thank you.

[Rob Williams]

I would not recommend adding more ram to your PC... there's just no need. You are not experiencing any performance issues now... so why bother? I'd overclock it before purchasing anymore ram... better performance > more ram that you won't use.

I tried out PAE in 32-Vista... still shows 2.75GB with 4.00GB installed. Not worth the time and effort to get it working. I'd just stay with what you have, personally.