4GB RAM installed, MAC showing 4GB, win 3GB, AE mac 3GB, AE 2GB how?

kwfl

macrumors 6502
Original poster
Aug 20, 2007
403
0
i got the aliuminium 24'' 2.8GHz with 2GB ram

i upgraded it to 4GB from OWC
in mac sys profiler it is showing 4GB
in windows installed via boot camp, showing 3GB
in after effects (when it starts up, it shows u the memory available and used) in MAC it is showing only 3GB, and AE in windows showing only 2GB

anyone can explain?
 

aaronw1986

macrumors 68030
Oct 31, 2006
2,607
0
32 bit versions of windows will only display the 3gb of ram, so that's normal. Programs can't utilize all the RAM, so that's why it's prob showing up less for that.
 

kwfl

macrumors 6502
Original poster
Aug 20, 2007
403
0
thanks for ur help

i installed windows vista yester on a MBP with 4GB ram too
vista showing only 3GB too

i thought they resolved ram problem in Vista.
 

Narg

macrumors member
Jan 23, 2008
93
42
Gees guys, you all have it wrong.

The real issue in an Intel issue, no the OS. And is caused/resolved by the BIOS.

In all computers, all components must be addressable in main memory or they cannot recieve data from the CPU. Most parts don't use much memory, but some use a lot. The Video card is one main culprit in most cases. Hard drive interfaces and other parts also take address space. So if you have a 512Megabyte video card, you are going to loose at least 512 Meg from your memory if you are using all 4 gig addressing space allowed by Intel chips in 32-bit mode. The video memory is mapped over the top of the RAM on your system, therefore lowering the amount of available memory to the OS. Some BIOS systems allow for 64-bit addressing outside of the OS, and can actively switch the memory addressing to allow a 32-bit OS to access all 4 gigabytes. This is was the Apple BIOS does when OSx is running on the machine. It is also seen on some systems running 32-bit Windows, but not all. It's all up to the BIOS.

When running a Microsoft OS on an Apple, the BIOS is virtualized in memory via Boot Camp and is only a 32-bit BIOS image. Therefore no re-mapping of video or other used memory is available. So the amount of RAM available to the OS is reduced. If anyone, you should blame this on Apple for not providing a BIOS under Boot Camp that can re-map higher memory to allow access to all 4 gigs of ram. 64-bit Windows versions will also have issues with 4 gig of RAM not showing if the BIOS does not allow for the re-mapping. Most laptop computers suffer from this problem, as they all seem to use 32-bit BIOSes only.

It's all due to the design made by Intel, and how good a BIOS is under your OS. Boot Camp's PC BIOS is to blame here.
 

Eidorian

macrumors Penryn
Mar 23, 2005
29,085
288
Indianapolis
Gees guys, you all have it wrong.

The real issue in an Intel issue, no the OS. And is caused/resolved by the BIOS.

In all computers, all components must be addressable in main memory or they cannot recieve data from the CPU. Most parts don't use much memory, but some use a lot. The Video card is one main culprit in most cases. Hard drive interfaces and other parts also take address space. So if you have a 512Megabyte video card, you are going to loose at least 512 Meg from your memory if you are using all 4 gig addressing space allowed by Intel chips in 32-bit mode. The video memory is mapped over the top of the RAM on your system, therefore lowering the amount of available memory to the OS. Some BIOS systems allow for 64-bit addressing outside of the OS, and can actively switch the memory addressing to allow a 32-bit OS to access all 4 gigabytes. This is was the Apple BIOS does when OSx is running on the machine. It is also seen on some systems running 32-bit Windows, but not all. It's all up to the BIOS.

When running a Microsoft OS on an Apple, the BIOS is virtualized in memory via Boot Camp and is only a 32-bit BIOS image. Therefore no re-mapping of video or other used memory is available. So the amount of RAM available to the OS is reduced. If anyone, you should blame this on Apple for not providing a BIOS under Boot Camp that can re-map higher memory to allow access to all 4 gigs of ram. 64-bit Windows versions will also have issues with 4 gig of RAM not showing if the BIOS does not allow for the re-mapping. Most laptop computers suffer from this problem, as they all seem to use 32-bit BIOSes only.

It's all due to the design made by Intel, and how good a BIOS is under your OS. Boot Camp's PC BIOS is to blame here.
I'm still reading 3 GB under Santa Rosa on XP x32. The GM965 chipset can address to 8 GB.

I'll try Ubuntu 64-bit when I get home.
 

geekrebel

macrumors newbie
Mar 5, 2008
2
0
Maximum 3GB RAM in Windows

Gees guys, you all have it wrong.

The real issue in an Intel issue, no the OS. And is caused/resolved by the BIOS.
That's complete bogus Narq!

You may take ANY x86 PC out there and install either Linux or Windows on it. Unless you're running 64-bit versions of the OS, you will not see more than about 3GB of RAM.

Here's a brilliant article explaining why: http://www.dansdata.com/askdan00015.htm
 

bluegoo26

macrumors newbie
Dec 22, 2004
5
0
I found this thread because I had the same question, but more specifically about After Effects. I get the basic idea of why Windows only uses 3 of my installed 4, but why does After Effects also?

Thanks.
 

Attachments

The Flashing Fi

macrumors 6502a
Sep 23, 2007
763
0
Read this. It explains why apps only see 2Gb even if there is more physical RAM installed. Basically it's down to Windows suckage.
It has nothing to do with Windows suckage. It's a restriction in 32-bit OSes in general. Linux faces the same problem with kernel's not compiled to utilize PAE. There is only 4 gigs of available address space. So any type of memory (like video card memory) takes away from the total amount of RAM.

One of the work arounds is through the use of PAE (Physical Address Extension).

Some BIOSes provide work arounds on PCs, others don't. Apple needs to get off their tail and put out 64-bit drivers for all their computers.

Anyway, back to my point. The limitation is in 32-bit OSes. There are work arounds, but sometimes, they're not pretty.

Anyway, this is an article about PAE in Vista:

http://msdn2.microsoft.com/en-us/library/aa468629.aspx

If you have Data Execution Protection enabled, PAE is enabled.

Personally, I wouldn't mess with anything, unless you know what you're doing.
 

agojes

macrumors member
Jan 5, 2008
46
0
Indonesia
I have the same problem myself. This week I installed 4GB in my Merom SR MBP. I got a reading of 4GB from my OSX but the reading is 3GB in Vista (Boot Camp).

I thought Microsoft resolve this issue with Vista that it can handle 4GB of memory? I know XP can't handle more than 3GB, but doesn't Vista supposed to be able to handle more than 3GB? Or I got it all wrong from the beginning? :p

I'm no computer expert, but I was just wondering if Vista is indeed using full 4GB or just 3GB of the RAM? Even though the reading is just at 3GB?

Anyone can explain this will be appreciated.
 

The Flashing Fi

macrumors 6502a
Sep 23, 2007
763
0
I have the same problem myself. This week I installed 4GB in my Merom SR MBP. I got a reading of 4GB from my OSX but the reading is 3GB in Vista (Boot Camp).

I thought Microsoft resolve this issue with Vista that it can handle 4GB of memory? I know XP can't handle more than 3GB, but doesn't Vista supposed to be able to handle more than 3GB? Or I got it all wrong from the beginning? :p

I'm no computer expert, but I was just wondering if Vista is indeed using full 4GB or just 3GB of the RAM? Even though the reading is just at 3GB?

Anyone can explain this will be appreciated.
Wait until SP1 is released to the general public (supposed to be this month and at most next month).
 
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