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You are here: MacNN Forums > Software - Troubleshooting and Discussion > Alternative Operating Systems > Mac Pro with 3GB RAM shows up as 2GB under Windows XP

Mac Pro with 3GB RAM shows up as 2GB under Windows XP
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Jan 10, 2007, 12:37 AM
 
In Windows XP, my Mac Pro shows as having only 2 GB of virtual memory when I have 3 GB. This system came with 1 GB, and I added 2GB of memory today. I put the new memory on the topmost card by first removing the original 512MB x 2. I then installed the 512MB x 2 in the bottom memory card. All RAM is in slots 1 and 2, in pairs. Dimm slots 3 and 4 have nothing on either card. In other words, the RAM is installed correctly. I may try switching the memory so that the top card has the 512's, and the bottom has the 1024's.

Windows shows that there are indeed 3072.00 MB of physical memory, which is available running Microsoft Office and clicking help, about, System Info. Available Virtual Memory is 1.96GB. Available Physical memory is 1.61GB. Where is my third GB? Any issues with this motherboard and 3GB of RAM? I thought it was an Intel board, so this should mean it will work. I updated everything on the machine under Mac OS X before installing Windows a few weeks ago. SMBIOS version says 2.4. BIOS Version and date says

BIOS Version/Date Apple Computer, Inc. MP11.88Z.005C.B04.0610131226, 10/13/2006

Four processors are listed, MacPro 1.1 is the system model.

All of that comes from System Info in Windows.

Mac OS X of course reports 3GB of memory in About this Mac.

Don't use the size tag! OreoCookie
( Last edited by OreoCookie; Jan 17, 2007 at 08:52 AM. )
     
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Jan 15, 2007, 09:25 PM
 
I have heard rumors that WInXP will only see and use 2gb of ram, any more in a WinXP machine is useless.
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Jan 16, 2007, 11:46 AM
 
Silverflyer is right Windows XP will only use 2 GB of ram. I have 3GB but when I boot to XP it only see's 2 gb. Windows XP x64 will see all of you memory but unfortunately boot camp does not supply drivers for it.
Mac Pro 2.66 GHz/ 3GB of RAM / 250GB HD/ 320GB HD/ 320GB external FW800 HD / Geforce 7300GT / Dual 19" Acer LCD (4.3)
     
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Jan 16, 2007, 01:39 PM
 
Actually, Silverflyer is wrong.

The total amount of memory (Physical and Virtual) WinXP can support is 4GB. The reason you are only seeing 2GB of physical memory used, is because you have a 2GB swap. You can have XP recognize the third gig, by using the /3GB switch in your boot.ini file:
Memory Support and Windows Operating Systems

This should work on a Mac system running windows through bootcamp. I'm not sure, as I dont have bootcamp installed on my MacPro, but on my 8GB Opteron box (dual booted between linux and WinXP), the /3GB switch set my virtual memory to 1gb, and thus recognizes a third gig of physical memory.
     
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Jan 16, 2007, 07:36 PM
 
Mark, I tried what you suggested; I lowered my virtual memory to 1 GB and set the /3G switch in the boot.ini file. When I right clicked my computer to get system properties it still shows me 1.98 GB RAM, however I got different results when I ran msinfo32.exe

without the /3GB switch I get this:
.
.
.
Total Physical Memory 3,072.00 MB
Available Physical Memory 1.63 GB
Total Virtual Memory 2.00 GB
Available Virtual Memory 1.96 GB
Page File Space 2.83 GB
...


with the /3GB switch:
.
.
.
Total Physical Memory 3,072.00 MB
Available Physical Memory 1.70 GB
Total Virtual Memory 3.00 GB
Available Virtual Memory 2.96 GB
Page File Space 2.89 GB
...

To be honest I'm more confused then ever. In both test my virtual memory is set to 1 Gb and in both instances it does report my total physical memory, yet with the /3GB switch the virtual memory has an extra gig. It seems to be treating the extra ram as virtual memory.
( Last edited by davidrivera; Jan 16, 2007 at 09:30 PM. )
Mac Pro 2.66 GHz/ 3GB of RAM / 250GB HD/ 320GB HD/ 320GB external FW800 HD / Geforce 7300GT / Dual 19" Acer LCD (4.3)
     
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Jan 16, 2007, 11:50 PM
 
Try downloading pc wizard and check the total memory installed. I think windows does have the 3 GB installed, BUT your mobo requires a BIOS update to recognize it. This problem is common on some manufacturers of PCs.
     
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Jan 17, 2007, 12:52 AM
 
The 3GB machine is my Mac Pro and I do have 3GB cause I see it on OS X but I will download pc wizard it may give better clue whats going on.
( Last edited by davidrivera; Jan 17, 2007 at 01:10 AM. )
Mac Pro 2.66 GHz/ 3GB of RAM / 250GB HD/ 320GB HD/ 320GB external FW800 HD / Geforce 7300GT / Dual 19" Acer LCD (4.3)
     
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Jan 17, 2007, 02:04 AM
 
Originally Posted by polendo View Post
Try downloading pc wizard and check the total memory installed. I think windows does have the 3 GB installed, BUT your mobo requires a BIOS update to recognize it. This problem is common on some manufacturers of PCs.
thats an odd reply for a mac forum, especially considering the OP was specifically asking about his Mac Pro...
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Jan 17, 2007, 08:26 AM
 
If you are running standard XP, its 32-bit which will not use more than 2GB of RAM, just like a 32-bit Mac. You need Windows XP64, or Vista or one of the 64 bit server versions to get more than 2GB I would think.
     
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Jan 17, 2007, 08:53 AM
 
This is a Windows problem, moving …
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Jan 17, 2007, 06:49 PM
 
Actually is more like a mac hardware issue affecting a windows restriction.
     
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Jan 17, 2007, 07:00 PM
 
Odd that this thread was sort of highjacked, but that's good that it's more or less on topic. Anyway, I did a little testing. First off, folks, the /3GB switch in boot.ini has no effect on the memory recognition of Windows, EVER. This is not a software memory usage issue, which is what /3GB changes -- the ability of software programs to use more than 2GB of memory.

But I did try, as a possible solution, another switch in the boot.ini. When you look at the System Properties of the Mac Pro, it says "Physical Address Extension" or PAE. This is because WinXP will turn PAE on if you install service pack 2 from scratch like I did with Boot Camp beta. Turning it off is not simple, so I RTFM. I had to use this switch: /NOEXECUTE=ALWAYSOFF to turn off the noexecute abilities, and then I went ahead and used /NOPAE just in case (they say you don't have to do that, per se, but I did) Well, turning off PAE did not help, as I sort of guessed. I had not seen it work for anyone else, but I tried that, just in case. When I booted back up, there was no PAE running, but the memory report was the same as I reported in my first post.

So scratch any boot.ini edits. It is essentially a BIOS issue, not allowing Windows XP 32-bit access to memory above 2GB on the Mac Pro. This is essentially a known issue with the Mac Pro, and I wish that Apple would come out with an official recognition of the problem. If I had a contact at Apple that would act on this, perhaps I could at least ask for this much:

(Apple could post a notice such as this in a FAQ.)

32-Bit versions of Microsoft Windows XP Home and Windows XP Professional will not utilize more than 2GB of RAM on the Mac Pro. You must use a 64-bit version of Windows to utilize more than 2GB of memory on this system.

This is until there is a BIOS update from Apple, which will never come. There are a lot of systems in the world which have a limit of 2GB, 3GB, or 3 and a half GB, or something like that in Windows. I think it's a bad deal that the humongous Mac Pro with room for 16 GB of this fancy fully-buffered memory is limited to just 2GB under Windows, but I doubt it will change unless I install Vista 64-bit. Likely to be forgotten eventually, but for now the whole world is used to running 32-bit everything, so this problem will come up a lot in the next three years as people try doing this.

I'm not sure how this applies to other Intel-based Macs or other Windows versions like Vista or Server 2003. I should be able to obtain Vista soon and test it out soon. I have server, but I need time to test it.
     
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Jan 17, 2007, 07:28 PM
 
Originally Posted by Microsoft
Operating systems based on Microsoft Windows NT technologies have always provided applications with a flat 32-bit virtual address space that describes 4 gigabytes (GB) of virtual memory. The address space is usually split so that 2 GB of address space is directly accessible to the application and the other 2 GB is only accessible to the Windows executive software.

...snip...

Windows XP Professional and Windows Server 2003 Memory Support. The maximum amount of memory that can be supported on Windows XP Professional and Windows Server 2003 is also 4 GB. However, Windows Server 2003, Enterprise Edition supports 32 GB of physical RAM and Windows Server 2003, Datacenter Edition supports 64 GB of physical RAM using the PAE feature.

The virtual address space of processes and applications is still limited to 2 GB unless the /3GB switch is used in the Boot.ini file. When the physical RAM in the system exceeds 16 GB and the /3GB switch is used, the operating system will ignore the additional RAM until the /3GB switch is removed. This is because of the increased size of the kernel required to support more Page Table Entries. The assumption is made that the administrator would rather not lose the /3GB functionality silently and automatically; therefore, this requires the administrator to explicitly change this setting.
It would seem that a mere tweak of the boot.ini file is what's called for on the Mac Pro. Can someone try this and report back the (probable) positive results?

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Jan 17, 2007, 08:27 PM
 
Negative. No. Does not work, nor is it meant to work. I am trying to get this type of misinformation promulgated to Mac users: the switch for /3GB has nothing, repeat, nothing to do with the operating system not using all installed RAM. It has everything to do with the way virtual memory space is allotted to two different subcomponents: the application and the "Windows executive software" or OS.

It is meant to provide a convenient, larger amount of memory to SOFTWARE that normallly only can obtain operating system allowance of just 2GB of virtual memory -- software like AutoCAD 2007 Between the Lines: AutoCAD 2007 and the /3GB Expanded Memory or Adobe Photoshop CS2 Memory allocation and usage (Photoshop CS2) - Support Knowledgebase
are some examples a user might be familiar with. An IT pro might have heard of Microsoft Exchange. Use of the /3GB switch in Exchange Server 2003 on a Windows Server 2003-based system PLEASE LOOK AT THOSE LINKS BEFORE YOU RESPOND, as they talk about the reason to use /3GB.

Notice that all of these talk about a piece of software that suggests you use this switch sometimes, and only for a particular reason. It is a bad thing to recommend or use the /3GB switch if you don't need it, because it effects the memory allotted to the OS. You can't change application memory positively unless you change the OS memory situation negatively. The sum of all virtual memory stays at 4GB on a 32-bit Windows. So by adding the /3GB switch, for apps, you are giving just 1 GB to you system. Bad, bad, unless you know what you are doing and have a need to do so.

Please, read those three webpages. There you will see that this /3GB switch is a neat thing for software and its ability to use large amounts of virtual memory, and hopefully you can understand that it has zero implications to detect your computer's physical memory.

Here is what it is for, using your link, sir, from Microsoft: "Application Memory Tuning. This capability allows memory-intensive applications to utilize up to 50 percent more virtual memory on Intel-based computers. Application memory tuning provides more of the computer's virtual memory to applications by providing less virtual memory to the operating system."
     
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Jan 17, 2007, 09:46 PM
 
<ducks behind large furniture>oops... I DID look at Microsoft's page, and still managed to see what wasn't there. To me it looked like a potential direction to investigate, and this particular issue was not mentioned previously, so I posted it. To be fair, I did not exhaustively research this issue, and I have never "needed" more than the 1GB of RAM in my MBP, so I am a newb when it comes to such large amounts of RAM and how they're used.

So anyway, to recap the overall issue: on PC hardware, XP can see the actual amount of RAM installed, report its size correctly and use it appropriately (up to its built-in 4GB limit). But on Mac hardware it sees only 2GB at most. XP MUST inquire about the amount of RAM through the hardware, so perhaps this is a hardware issue rather than a Windows issue. Is there chatter on Apple's boards about this?

Glenn -----OTR/L, MOT, Tx
     
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Jan 19, 2007, 07:32 AM
 
Anyone try adding /PAE to their boot.ini to enable PAE mode? I have to do this on my 2003 Servers that use 4GB of ram. Without it the OS only recognizes 3GB. Probably won't do anything as its meant to address more than 4GB of ram specifically. Worth a shot though. I've never run into XP not seeing more than 2GB.
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Jan 20, 2007, 05:17 PM
 
I work for a large 3D training centre & was really hoping to ditch our PC's for high-end Macs - unfortunatley we have to run 3D Studio Max w/Windows and they require a ton of ram. I recently bought 2 Mac Pro's with the Nvidia 4500's and have discovered the 2 gig limit. All of our PC's have the 3G switch.

So, what is the solution to run ram intensive PC-only applications?

- install 64 bit XP (will there be driver issues?)?
- buy Vista?
- cancel our Mac purchase and buy PC's - seriously?

I am willing to test out any possible solution to confirm on one of the dust collecting Mac Pro's.
     
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Apr 2, 2007, 02:19 PM
 
FYI, I just installed 32-bit Vista Home Premium and it still only recognizes 2GB on the 3 GB installed?
     
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Apr 2, 2007, 03:30 PM
 
Has anyone installed Vista 64-bit on these machines yet? Drivers?
     
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Apr 2, 2007, 05:56 PM
 
According to Microsoft, XP-Pro supports 4GB or physical RAM. Note that under the "Page File" section of this page, it mentions that each process has its own 2GB virtual memory space-I wonder if this is causing the effects that are being reported here. Has anyone tried using a dedicated Windows XP RAM testing program to determine whether the extra gig of RAM is actually seen and not ignored?

Glenn -----OTR/L, MOT, Tx
     
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Apr 3, 2007, 04:50 PM
 
Originally Posted by Eug View Post
Has anyone installed Vista 64-bit on these machines yet? Drivers?
If you can find signed 64-bit drivers, otherwise they won't load.
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Apr 24, 2007, 07:42 PM
 
Originally Posted by Dewey View Post
I work for a large 3D training centre & was really hoping to ditch our PC's for high-end Macs - unfortunatley we have to run 3D Studio Max w/Windows and they require a ton of ram. I recently bought 2 Mac Pro's with the Nvidia 4500's and have discovered the 2 gig limit. All of our PC's have the 3G switch.
I'm annoyed with this 2GB limit as well...I got my Mac Pro with 4GB of RAM because I use geological mapping software that uses a lot of computing power and I was hoping to get it running faster than it had been on my older PC. Let's hope Apple's next release of Boot Camp has 64-bit Windows drivers...maybe we should all e-mail their Boot Camp feedback about this to encourage it?

On another note, is anyone having trouble seeing both procs under XP Pro? My computer only recognizes one...
     
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Apr 28, 2007, 02:57 PM
 
Well, I'm using Vista Home Premium on a Mac Pro 2,66Ghz with 5Ghz of RAM, and it detects only 2GB (not even 4GB). I hoppe that this will be fixed on future Bootcamp updates. I don't feel like installing Vista 64Bit and have to deal with compatibilty issues with drivers, games etc...
     
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Apr 30, 2007, 12:56 PM
 
Originally Posted by machou View Post
Well, I'm using Vista Home Premium on a Mac Pro 2,66Ghz with 5Ghz of RAM, and it detects only 2GB (not even 4GB). I hoppe that this will be fixed on future Bootcamp updates.
OK you're running Vista, question then, what version of Bootcamp are you using? On page 4 of the Boot Camp 1.2 manual, it says that 2GB or more RAM is required with Vista on the MacPro...

I posted this in a thread that has been pretty much ignored so far:
http://forums.macnn.com/104/alternat...1-2-solve-2gb/

Why would they require 2 GB RAM --OR MORE-- in BC 1.2 if it still won't be recognized???
( Last edited by justmetoo; Apr 30, 2007 at 01:03 PM. )
     
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Apr 30, 2007, 04:45 PM
 
Originally Posted by justmetoo View Post
I posted this in a thread that has been pretty much ignored so far:
http://forums.macnn.com/104/alternat...1-2-solve-2gb/
Not ignored, just discussed to an impasse. So far NOBODY can figure out either how to make even a Mac Pro see and use more than 2GB in XP/Vista, nor why Boot Camp 1.2 says "2.0GB or more" in its suggested configuration for the MP.

I'd LOVE to have THE answer for you! But not only do I not have a Mac Pro, I don't have any way to get Apple to talk to me about the issue that hasn't already been used and posted here-without a resolution to this issue.

Glenn -----OTR/L, MOT, Tx
     
   
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