Memory limitations in 32-bit systems

Dr Zaius

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Here is a link to a very interesting article on the "3GB" memory limitation for 32-bit operating systems.

Dell, Falcon Northwest and numerous other high-end computer makers sell systems with 4GB of RAM and duel Geforce 7950 Nvidia graphics cards (i.e., quad SLI). This could be a bad setup according to this article.

Ask Dan: What's with the 3Gb memory barrier?
 

Redwolf

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Woah. That article is extremely misleading.

Here's the real deal.

To make use of 4 GB or more RAM in a 32 bit OS you have to have:
  • a BIOS that successfully remaps the space from 3-4 GB to 4-5 GB (because that space is taken by devices and the RAM there needs to be remapped).
  • working PAE to make use of the memory above 4 GB (independently of whether you have more than 4 GB RAM or whether you have remapped memory of your 4GB kit living above 4GB addresses).
That's all. It is true that Mickeysoft has decided to by default disable working PAE in XP SP2, but it did have working PAE in before SP2, and other 32 bit Windozes like Win2K also have working PAE. Needless to say, all of Linux, FreeBSD and NetBSD have working PAE.

Since I don't use it I haven't tried first-hand, but I have been told that manually activating PAE in SP2 works fine, except that many many drivers are written violating Microsoft's requirements (which include proper support of PAE).

If you miss the proper remapping support (point 2), then you will permanently lose memory that is from 3-4 GB, how much depends on what PCI/AGP/PCIe cards exactly you have installed. Example: you have 4 GB, no working remapping and 724 MB worth of devices the OS wants reserved, then you have 3.3 GB usage. You have 6 GB RAM, no working remapping and 1 GB worth of devices, then you get 5 GB (you lose the space between 3-4 GB). If you have 6 GB and working remapping, and 1 GB worth of devices, then you get 6 GB - because the remapping now has memory living at 0-3.0 GB and 4.0-7.0 GB, because the memory in the space between 3-4.0 GB (the space used by devices), has now not been deactivated, but remapped.

%%

Now, all the above is about physical memory, aka RAM. In addition there are limitations in virtual memory o 32 bit OSes, which manifest themselves in how much virtual memory each userlevel process can take, but mapping X MB of virtual memory still can mean much less, or even much more, actual physical memory (RAM). But that's not the topic here.
 
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Dr Zaius

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So what is your opinion of 32-bit gaming rigs that come armed to the teeth in the graphics department? Specifically, I'm thinking of systems that use various configurations of SLI or quad SLI with cards that have 512 RAM or better. That earlier article strongly suggests such systems are very likely a bad idea because of the memory limits.
 

Redwolf

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So what is your opinion of 32-bit gaming rigs that come armed to the teeth in the graphics department? Specifically, I'm thinking of systems that use various configurations of SLI or quad SLI with cards that have 512 RAM or better. That earlier article strongly suggests such systems are very likely a bad idea because of the memory limits.
Well, the big question is whether Mickeysoft hard disabled PAE in XP SP2. That is what several people claim, among others the authors of the above article.

I have been told, however (remember I don't use Windows outside gaming, much less XP, so I don't have first-hand experience), that this is nonsense and that you can activate it if all your drivers are properly coded. That rules out all that Creative junk and many Nvidia chipset (not graphics) drivers, but for most other systems, Intel chipset (chipset, not CPUs) systems in particular, you can have hope.

So, to sum up, I'd just try re-activating PAE when using 4 GB. Of course, as mentioned in my previous post, you also need working remapping in the BIOS.

%%

Alternatively you can use XP SP1 or Windows 2000 (that's what I have on my gaming box) or some 64 bit Windows.

Failing everything, buying 4 GB and using only 3-3.3 isn't that bad a deal either, and later when you update to a real OS or to 64 bit Windows you get your memory back. Mixing 2x1GB + 2x 512 MB looks more efficient buying-wise but can be problematic with some mainboards. 3 GB is certainly better than 2, in particular if you are shuffling 0.5-1.0 GB of texture memory around all the time.
 

Dragon2611

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Aren't all current gen Proccessors 64bit anyway (i.e althon64 x2 and core2)

I've heard rumors that if you buy a pc running vista and it comes with 32bit you can install vista 64bit and use the licence key that comes with your pc and it will still activate fine.
 

Redwolf

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Aren't all current gen Proccessors 64bit anyway (i.e althon64 x2 and core2)
The last major chip to not have 64 bits was the Intel mobile Core Duo, found in many laptops, even today and some mini Macs. Only the Core 2 Duo introduced 64 bits.

Intel's single-core mobile chips are all 32 bits only.

I've heard rumors that if you buy a pc running vista and it comes with 32bit you can install vista 64bit and use the licence key that comes with your pc and it will still activate fine.
Who cares? :)
 

Dragon2611

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The last major chip to not have 64 bits was the Intel mobile Core Duo, found in many laptops, even today and some mini Macs. Only the Core 2 Duo introduced 64 bits.

Intel's single-core mobile chips are all 32 bits only.



Who cares? :)
Errm if its a new system (which usally comes preinstalled with vista32) and you want to put 4gb or more of ram in it then you might as it saves you paying for vista again.

of course you could just run linux (which reminds me i need to reinstall ubuntu)
 

Redwolf

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You don't need a 64 bit OS for more than 4 GB RAM, you just need working PAE in your 32 bit OS. Microsoft removed it in XP SP2, but I assume Vista has it.
 

Dragon2611

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You don't need a 64 bit OS for more than 4 GB RAM, you just need working PAE in your 32 bit OS. Microsoft removed it in XP SP2, but I assume Vista has it.
no idea not looked.
 

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Aren't all current gen Proccessors 64bit anyway (i.e althon64 x2 and core2)
Depends on whether you mean address or data width.

Data width - Athlon Tbird and Pentium 3 onwards.

Address width - I don't think desktops have true 64bit addressing. They advertise it, but it's limited to... 40 or 48.

Just more than 32, ie not limited to 4GB total memory space.

I've heard rumors that if you buy a pc running vista and it comes with 32bit you can install vista 64bit and use the licence key that comes with your pc and it will still activate fine.
Why would you want to? Give Vista a couple of years to shake the bugs out.
 
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Dragon2611

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Depends on whether you mean address or data width.

Data width - Athlon Tbird and Pentium 3 onwards.

Address width - I don't think desktops have true 64bit addressing. They advertise it, but it's limited to... 40 or 48.

Just more than 32, ie not limited to 4GB total memory space.


I've heard rumors that if you buy a pc running vista and it comes with 32bit you can install vista 64bit and use the licence key that comes with your pc and it will still activate fine.
Why would you want to? Give Vista a couple of years to shake the bugs out.[/QUOTE]

You obviously know more about me when it comes to 64bit addressing.. As for vista well if it came with your new pc then you have it anyway so why not try 64 if it aint gonna cost anything...
 

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It's down to how Windows is now distributed with a new branded PC. Has been like this since optical burner drives came as standard...

... instead of getting a true Windows Install disk, like you get with buying Windows seperately, the manufacturer supplies a "restore" procedure - you have to burn your own disks. And all they do is restore the machine to how it was from the factory. You may or may not get an option to back data up first.

I use different versions of Windows (and sometimes other OS) ON THE SAME MACHINE.

You just can't do that with Restore disks. Oh yeah, and if the machine makes a pigs ear out of making the Restore disks, then tough. The manufacturer won't supply them seperately UNLESS YOU PAY FOR THEM.

This is why I'm pretty much against upgrading to a new OS until at least a couple of years have passed. The price drops as well. ;)

Why upgrade just to help Microsoft find their own mistakes? Bearing in mind that all the software in that time doesn't even need Vista?

I appreciate the reality in my country isn't reflected everywhere... but one old proverb sums it up well.

"If it ain't broke - don't try to fix it."
 

jayedub7423

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so i have a question, I just upgraded to an AMD Athlon 64 X2 3800+, so would upgrading from 32-bit win xp to 64-bit xp make a difference for me?
 

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IF you plan on attaching a lot of memory - for instance, Adobe Photoshop loves lots of RAM - then it would make sense.

If you are expecting a massive speed improvement - forget it. It's not going to be any faster at all.

Oh, XP 64 bit is incompatible with many pieces of hardware - drivers need to be 64 bit friendly.
 
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