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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

195 replies

Loner T

Level 9

59,477 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

59,477 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

59,477 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 11, 2015 11:23 AM in response to Loner T

My structure looks exactly like yours however after booting a couple of times (after using the fdisk and bless command like before) now I only get the blinking cursor without any error message.

Loner T

Level 9

59,477 points

Jun 11, 2015 12:34 PM in response to Mortandos

Does disk0s1 show up in System Preferences -> Startup Disk?

Mortandos Author

Level 1

4 points

Jun 11, 2015 1:39 PM in response to Loner T

Not now, now. I rebooted and I had to the SRC / NVRAM reset in order to be able to boot from the SSD again. After using the fdisk and bless command, should it show there? And what if not?

Loner T

Level 9

59,477 points

Jun 11, 2015 3:06 PM in response to Mortandos

It is supposed to show as bootable device.

Mortandos Author

Level 1

4 points

Jun 11, 2015 3:36 PM in response to Loner T

I just ran fdisk and the bless command again, the disk0s1 doesn't show under STARTUP DISK, only the SSD drive.

Loner T

Level 9

59,477 points

Jun 11, 2015 5:03 PM in response to Mortandos

One option to test is to convert disk0s1 to NTFS and test booting.

Mortandos Author

Level 1

4 points

Jun 11, 2015 5:37 PM in response to Loner T

I just tried that, but the result is the same, the blinking cursor. After rebooting and holding the option key not even the efi boot is shown as usual.

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

59,477 points

Jun 13, 2015 12:00 PM in response to Mortandos

The VMware-based solution is the one I would recommend.

Loner T

Level 9

59,477 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.

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