Maximum RAM for Boot Camp on MacPro

[NedMacPro]

I have 5 GB RAM that shows up just fine on the OS X but in Boot Camp it is only showing 1.98...anybody know why?

[Anonymous Freak]

I have 5 GB RAM that shows up just fine on the OS X but in Boot Camp it is only showing 1.98...anybody know why?

Because Windows XP Home and Professional editions are only 32-bit, they have an inherent limitation of 4 GB. However, by default, they only show up to 2 GB as 'user-addressable'. This can be increased to 3 GB by adding the '/3GB' switch to your boot.ini listing. Usually, XP reserves anything over 2 GB for system use. (And, yes, 3 GB is the absolute max that XP Pro will allow to be seen by applications.)

See here (http://www.microsoft.com/whdc/system/platform/server/PAE/PAEmem.mspx), 4th through 7th paragraphs.

Another possible workaround is to install the 64-bit version of Windows, Windows XP Professional x64 Edition (http://www.microsoft.com/windowsxp/64bit/default.mspx). (Although I don't know if Boot Camp supports it...)

[dextertangocci]

The problem:

windoze;) :rolleyes:

Is it the 32 bit version of xp? If so, I think it will only recognise 4GB RAM.

I hve no idea why it doesn't evn recognise 2:confused:

[NedMacPro]

Thx for the info...I will try this...Because Windows XP Home and Professional editions are only 32-bit, they have an inherent limitation of 4 GB. However, by default, they only show up to 2 GB as 'user-addressable'. This can be increased to 3 GB by adding the '/3GB' switch to your boot.ini listing. Usually, XP reserves anything over 2 GB for system use. (And, yes, 3 GB is the absolute max that XP Pro will allow to be seen by applications.)

See here (http://www.microsoft.com/whdc/system/platform/server/PAE/PAEmem.mspx), 4th through 7th paragraphs.

Another possible workaround is to install the 64-bit version of Windows, Windows XP Professional x64 Edition (http://www.microsoft.com/windowsxp/64bit/default.mspx). (Although I don't know if Boot Camp supports it...)

[Trip.Tucker]

Accepted answer:

Because Windows XP Home and Professional editions are only 32-bit, they have an inherent limitation of 4 GB. However, by default, they only show up to 2 GB as 'user-addressable'. This can be increased to 3 GB by adding the '/3GB' switch to your boot.ini listing. Usually, XP reserves anything over 2 GB for system use. (And, yes, 3 GB is the absolute max that XP Pro will allow to be seen by applications.)

See here (http://www.microsoft.com/whdc/system/platform/server/PAE/PAEmem.mspx), 4th through 7th paragraphs.

Another possible workaround is to install the 64-bit version of Windows, Windows XP Professional x64 Edition (http://www.microsoft.com/windowsxp/64bit/default.mspx). (Although I don't know if Boot Camp supports it...)

[CanadaRAM]

the /3GB switch in Windows on a PC affects only the amount of RAM that is allocatable to applications (and only if the application is coded to take advantage of it, few are), not the total RAM visible / usable by the OS.

The Bootcamp / EFI firmware of the Mac Pro limits the RAM Usable in 32-bit Windows to 2 GB. The /3GB and PAE switches have nothing to do with the amount of RAM accessible by Windows under Bootcamp.

[mosx]

the /3GB switch in Windows on a PC affects only the amount of RAM that is allocatable to applications (and only if the application is coded to take advantage of it, few are), not the total RAM visible / usable by the OS.

The Bootcamp / EFI firmware of the Mac Pro limits the RAM Usable in Windows to 2 GB. The /3GB and PAE switches have nothing to do with the amount of RAM accessible by Windows under Bootcamp.

Exactly.

Also, the 32-bit version of Windows (XP and Vista) can address 3GB. Not 2GB.

Seeing less than 3GB when 3GB or more is installed is always the fault of the chipset, not the OS.

64-bit Windows can address 4GB and above. Vista Home Premium has something like a 16GB limit.

[nurfen]

The Bootcamp / EFI firmware of the Mac Pro limits the RAM Usable in Windows to 2 GB. The /3GB and PAE switches have nothing to do with the amount of RAM accessible by Windows under Bootcamp.

What? So, if I run Vista x64, I still can't use my 6 GBs of RAM?

[617arg]

What? So, if I run Vista x64, I still can't use my 6 GBs of RAM?

You can. When I run Vista x64 through Bootcamp I can see all 18GB of my RAM. When I'm running through Fusion I have 8GB allocated, and it shows up.

[Siron]

I have Vista Business (to use 8 cores) 64 bit (to see all RAM - I have 4GB and it sees all of it). My XP Pro 32 only saw 3GB. Go with Vista Business 64. Forget about the 'Vista sucks' posts - I have had no problems whatsoever and it runs faster than XP 32.
Alan

[steveza]

Agreed - get Vista x64 (any version other than Home Basic/Premuim) and your RAM and processors will be available to you.