Level 1

4 points

Why can I only use 2.48 GB RAM in Boot Camp (Win 8.1 Pro, 64-bit)?

Hello, I am fairly new to the iMac and I have to use some programs in Windows that are not available for Mac so I set up Boot Camp and installed Windows 8.1.

My iMac is a I7-2600 CPU @ 3.4GHz with 16 GB RAM, system type-bit. Under system in Windows it shows Installed memory (RAM) 16 GB (2.48 GB usable).

I read about this problem and most answers are related to people using 32-bit. So what is wrong in my case, where is the problem?

Thank you in advance for help and suggestions.

iMac, OS X Yosemite (10.10.3)

Posted on May 3, 2015 11:52 AM

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Loner T

Level 9

59,536 points

Posted on May 4, 2015 8:04 PM

Your 2011 iMac is a preUEFI Mac (all Macs prior to Late 2013 models are). The preUEFI Macs support varying degrees of EFI boot capability, but do not fully comply with UEFI specifications. This causes various BC drivers to work, not work, or partially work, depending the year of the Mac and the OS used.

There are two methods that have been "successful" in working around broken Optical drives (apart from replacing it).

1. http://forums.macrumors.com/showthread.php?p=20584499#post20584499

2. Bootcamp without Optical disc drive

My recommendation is to remove Windows using BC Assistant (only, nothing else), and then try either of these two methods. You want a legacy BIOS installation (aka Hybrid MBR method). The CSM-BIOS layer correctly exposes hardware for preUEFI machines. It will also address your memory visibility issue.

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195 replies

Mortandos Author

Level 1

4 points

Jun 9, 2015 4:53 PM in response to Loner T

But you also had the same error message and the underscore cursor, I'm not sure whether the link regarding Windows 7 applies to my problem. Can you look at my previous post please and tell me the correct use of the bless and the fdisk command? The boot partition is disk0s1 (exFat) and the partition for the installation of Windows is disk0s2 (Tuxera NTFS), the hard disk is MBR.

Mortandos Author

Level 1

4 points

Jun 9, 2015 6:07 PM in response to Loner T

I started with the USB stick in the first place (that's how I did the EFI boot and that's (probably) why I only had 2.48 GB RAM available). So in case I want to use the USB stick the Fdisk command is for the USB stick and the bless command also?

Loner T

Level 9

59,536 points

Jun 9, 2015 6:24 PM in response to Mortandos

Your USB-related issue is because of the choice of EFI boot, not due to the USB itself.

The USB will only contain BC drivers, not the Windows installer. You have the following step in the link.

After partitioning has completed, click "Start the installation" and insert your Windows 7 install DVD. Your computer will restart.

In your case you will use the blessed disk0s1 instead of the Windows DVD. You can remove the '--nextonly' qualifier so you do not have to run this command multiple times.

Loner T

Level 9

59,536 points

Jun 9, 2015 6:59 PM in response to Mortandos

If you download the package, there is a file called AutoUnattend.xml. It sets up the Windows PE (Pre-boot Environment). It has the correct AMD drivers so the installer can be displayed. You can edit the file in a text editor and see how the drivers are loaded. These drivers are not bootable, but your disk0s1 is being marked bootable.

Loner T

Level 9

59,536 points

Jun 10, 2015 3:25 AM in response to improwise

improwise wrote:

This quickly turned into a Windows installation thread, was the original available RAM problem solved? Is it something specific to this/these Macs or affecting all Macs runnings BootCamp?

No. All Macs should work and recognize the available physical memory. Windows 32-bit cannot go beyond 3.84/4GB limit.

The issues discussed in this thread are

1. UEFI v BIOS booting

2. Lack of a functional Optical drive

3. iMacs with AMD GPUs not booting correctly due to lack of drivers

There is a separate PAE discussion which may become part of this discussion.

Mortandos Author

Level 1

4 points

Jun 10, 2015 8:10 PM in response to Loner T

Just to clarify this, you said "You need to put the contents of the .zip file at the root of disk0s1. It is kept separate to allow the Installer and the PE to be separate." but disk0s1 is the small boot partition. So BC drivers and Win install on the small partition?

Because in an earlier post you said "The USB will only contain BC drivers, not the Windows installer" - so WHERE do you want me to put the BC drivers?

I tried it with the BC drivers on the USB stick and got something new: This time I got the black screen with the message "Insert DVD or CD and press any key to return". So why did it want to boot from the super drive now?

Loner T

Level 9

59,536 points

Jun 10, 2015 8:47 PM in response to Mortandos

When a USB installer is used on newer Macs which support USB installers, the directory structure on the USB has two distinct parts, the contents of the Windows ISO or DVD and the $WinPEDriver$ folder and a Bootcamp folder.

For example, The ISO/DVD has

After BCA downloads Windows Support Software and combines it with the ISO, the structure becomes

In your case, by putting the $WinPEDriver$ folder and AutoUnattend.xml in the root folder makes your small partition have the same combination on a disk partition instead of a USB. This helps in loading drivers which are needed for the installation to work properly, by pre-loading drivers listed in the WinPEDriver folder. PE is the Pre-boot Environment for Windows.

Mortandos Author

Level 1

4 points

Jun 10, 2015 8:49 PM in response to Loner T

I'm now more confused than before, where do the BCA drivers go (stick or boot partition) and the AutoUnattend.xml is supposed to be on the stick (there is nothing else on the stick then? Just that one file???).

Loner T

Level 9

59,536 points

Jun 11, 2015 4:55 AM in response to Mortandos

When the BC drivers were on the USB stick, you got an error message, because you have the boot partition disk0s1 and the USB stick both as potential boot sources. If your Optical drive was working, you would still boot from the physical DVD, but since it is not there, you see the error message.

If you put the contents of the USB on to disk0s1 root directory, you will have a combined installer which has both BC drivers and Windows files, available from a single source device. You can then remove the USB at this point and try to boot from the internal disk0s1.

Mortandos Author

Level 1

4 points

Jun 11, 2015 9:31 AM in response to Loner T

Ok, so the .xml file in the root directory of the small partition and the BC drivers (in their original folder or also ALL SINGLE FILES in the root directory?), that's why I got confused when you wrorte

"My suggestion is to build the USB on a USB2 flash drive as recommended in the link and try your installation again." and then "You need to put the contents of the .zip file at the root of disk0s1. It is kept separate to allow the Installer and the PE to be separate.".

Loner T

Level 9

59,536 points

Jun 11, 2015 9:40 AM in response to Mortandos

Normally the DVD and USB are separate, but are being combined into disk0s1 because you do not have a working Optical drive.

Look at the second screen shot which has the DVD contents and the WinPEDriver folder combined. That is how your disk0s1 should look like. You can post a screen shot of the disk0s1 structure once you combine these, for verification purposes, if you like.

Mortandos Author

Level 1

4 points

Jun 13, 2015 11:42 AM in response to Loner T

Anything else I can try? I tried a cleaning disk in the super drive (again), it can read the music on the cleaning disc perfectly, it reads other CD's as well but refuses to read DVD's (I tried original Apple DVD's, I tried a few movie DVD's, nothing).

Or is there any way around the internal super drive (like tricking the computer to "believe" there is no internal one but use the external one?)?

Loner T

Level 9

59,536 points

Jun 13, 2015 2:52 PM in response to Mortandos

The largest file on the DVD is called install.wim which is

pwd

/Volumes/IRM_CCSA_X64FRE_EN-US_DV5/sources

ls -lh install.wim

-r-xr-xr-x 1 MyName staff 3.1G Aug 22 2013 install.wim

Copy all files from the DVD except this file to a CD and burn it. Boot from this CD. If you are prompted for the location of the install.wim, point it to your disk0s1 partition. Please test.

Mortandos Author

Level 1

4 points

Jun 14, 2015 1:13 PM in response to Loner T

But I cannot boot from my superdrive because it's broken.

Regarding your earlier post:

Parallels or VM ware? Unfortunately that's out of the question, much too slow (I actually tried that BEFORE I even came up with the whole Boot Camp idea).

Loner T

Level 9

59,536 points

Jun 14, 2015 2:31 PM in response to Mortandos

If you copy the DVD contents to a CD and exclude the install.wim, and try to boot from this CD, does it work? If the drive can read CDs but not DVDs, this is worth a test. You will waste a CD, if it does not work.

The other option is to use Rufus USB, burn the DVD to the USB and test if it can replace the DVD using Alt/Boot.

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Why can I only use 2.48 GB RAM in Boot Camp (Win 8.1 Pro, 64-bit)?