Mortandos
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Q: 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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Mortandos

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

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  • by Loner T,

    Loner T Loner T Jun 3, 2015 8:24 PM in response to Mortandos
    Level 7 (24,825 points)
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    Jun 3, 2015 8:24 PM in response to Mortandos

    The following method is worth a test, if you can get your friend's external Optical drive.

     

    1. Manually partition your internal disk.

    2. Manually create an MBR using this FAT partition.

    3. Connect the external DVD/Optical drive.

    4. Power cycle the iMac and hold the Alt Key. Select the Windows DVD.

    5. If the installer comes up, point it to this FAT partition which will be formatted to NTFS.

     

    You may run into Boot Camp: iMac displays a black screen during installation of Windows 7 - Apple Support, because of your AMD GPU.

  • by Mortandos,

    Mortandos Mortandos Jun 3, 2015 8:51 PM in response to Loner T
    Level 1 (0 points)
    Jun 3, 2015 8:51 PM in response to Loner T

    When I got the external drive that was the first thing I tried, holding ALT during startup but the external optical drive didn't show. Then I read that with iMac who who have an internal super drive it's not possible to boot from an external optical drive.

  • by Loner T,

    Loner T Loner T Jun 4, 2015 6:16 AM in response to Mortandos
    Level 7 (24,825 points)
    Safari
    Jun 4, 2015 6:16 AM in response to Mortandos

    I have used this procedure on 2008-2010 MBPs whose Optical drive was broken. Create a partition which is large enough to hold the ISO image that you have and add about 10% overhead. Use an external Optical drive and insert your physical media. Start Disk Utility and burn the DVD in the optical drive to this partition. Power cycle your Mac and hold the Alt Key. Do you see the newly created partition as a boot selection?

  • by Mortandos,

    Mortandos Mortandos Jun 4, 2015 9:19 AM in response to Loner T
    Level 1 (0 points)
    Jun 4, 2015 9:19 AM in response to Loner T

    Now I cannot format the internal drive anymore, it says partition failed, "couldn't open device".

  • by Loner T,

    Loner T Loner T Jun 4, 2015 9:22 AM in response to Mortandos
    Level 7 (24,825 points)
    Safari
    Jun 4, 2015 9:22 AM in response to Mortandos

    Can you see the 1TB drive in DU? Is it an exFAT format? Can you post the output of diskutil list?

  • by Mortandos,

    Mortandos Mortandos Jun 4, 2015 11:26 AM in response to Loner T
    Level 1 (0 points)
    Jun 4, 2015 11:26 AM in response to Loner T

    Yes, I see it in DU.

     

      Disk Description : ST31000528AS Media  Total Capacity : 1 TB (1,000,204,886,016 Bytes)

      Connection Bus : SATA  Write Status : Read/Write

      Connection Type : Internal  S.M.A.R.T. Status : Verified

      Partition Map Scheme : GUID Partition Table

  • by Loner T,

    Loner T Loner T Jun 4, 2015 11:30 AM in response to Mortandos
    Level 7 (24,825 points)
    Safari
    Jun 4, 2015 11:30 AM in response to Mortandos

    Does diskutil list show it?

  • by Mortandos,

    Mortandos Mortandos Jun 4, 2015 12:04 PM in response to Loner T
    Level 1 (0 points)
    Jun 4, 2015 12:04 PM in response to Loner T

    Yes:

     

    /dev/disk0

       #:                       TYPE NAME                    SIZE       IDENTIFIER

       0:      GUID_partition_scheme                        *1.0 TB     disk0

       1:                        EFI EFI                     209.7 MB   disk0s1

       2:                  Apple_HFS 1 TB                    999.9 GB   disk0s2

  • by Loner T,

    Loner T Loner T Jun 4, 2015 7:00 PM in response to Mortandos
    Level 7 (24,825 points)
    Safari
    Jun 4, 2015 7:00 PM in response to Mortandos

    If you do not have any data to preserve, can this disk be erased using the following command?

     

    diskutil eraseDisk exfat Windows disk0

  • by Mortandos,

    Mortandos Mortandos Jun 4, 2015 7:35 PM in response to Loner T
    Level 1 (0 points)
    Jun 4, 2015 7:35 PM in response to Loner T

    That worked, I can access disk0 again. Now the external optical drive is connected, the original Windows DVD is inserted, I click on BURN in DU and then what? It wants me to select a file, what am I supposed to select?

  • by Loner T,

    Loner T Loner T Jun 5, 2015 5:00 AM in response to Mortandos
    Level 7 (24,825 points)
    Safari
    Jun 5, 2015 5:00 AM in response to Mortandos

    Create a small partition on the internal 1TB disk of about 4+ GB. Using DU, burn the CD/DVD to this partition.

     

    Please see Disk Utility (Yosemite): Restore a disk image to a disk .

  • by Mortandos,

    Mortandos Mortandos Jun 5, 2015 7:54 AM in response to Loner T
    Level 1 (0 points)
    Jun 5, 2015 7:54 AM in response to Loner T

    I click on the optical drive with the Windows DVD, I click on restore, chose the destination (which is the small partition of disk0) and then I click on restore. That results in: Restore failure. Could not validate source - error 254

     

    I was following those steps:

     

    Restore a disk image with a single partition to a disk

    1. Select a disk in the sidebar, then click Restore.
    2. Drag the disk image to the Source field.You can drag the disk image from the list at the left, the Finder, or a web browser.
    3. Drag the disk that will hold the contents of the disk image to the Destination field.
    4. Click the Restore button.

  • by Loner T,

    Loner T Loner T Jun 5, 2015 8:20 AM in response to Mortandos
    Level 7 (24,825 points)
    Safari
    Jun 5, 2015 8:20 AM in response to Mortandos

    Are you clicking on the SuperDrive or the entry under the SuperDrive?

  • by Mortandos,

    Mortandos Mortandos Jun 5, 2015 8:55 AM in response to Loner T
    Level 1 (0 points)
    Jun 5, 2015 8:55 AM in response to Loner T

    The entry under the SuperDrive. I tried both but the restore button only appears when clicking on the entry under the Super Drive.

  • by Mortandos,

    Mortandos Mortandos Jun 5, 2015 3:25 PM in response to Loner T
    Level 1 (0 points)
    Jun 5, 2015 3:25 PM in response to Loner T

    I tried the following afterwards:

     

    /dev/disk0

       #:                       TYPE NAME                    SIZE       IDENTIFIER

       0:     FDisk_partition_scheme                        *1.0 TB     disk0

       1:               Windows_NTFS 1TB Boot                10.1 GB    disk0s1

       2:               Windows_NTFS 1TB Windows             990.1 GB   disk0s2

     

    sudo dd if=/Users/MSSD/Win81.iso of=/dev/rdisk0s1 bs=1m


    which resulted in

     

    4991+1 records in

    4991+1 records out

    5234294784 bytes transferred in 47.563281 secs (110049069 bytes/sec)

     

    The problem is: it's not on the 1TB partition (which is disk0s1).

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