Mortandos

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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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 May 4, 2015 8:04 PM in response to Mortandos
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    May 4, 2015 8:04 PM in response to Mortandos

    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.

  • by Mortandos,

    Mortandos Mortandos May 5, 2015 9:53 AM in response to Loner T
    Level 1 (0 points)
    May 5, 2015 9:53 AM in response to Loner T

    Ok, I will need some time to look into that. When starting the boot camp assistant I'm getting an error message though:

     

    The startup disk cannot be partitioned or restored to a single partition. I'm using an external SSD for MACOS, is there any disadvantage in formatting the internal HD (which is meant to be for Boot Camp / Windows manually?

  • by Loner T,

    Loner T Loner T May 5, 2015 10:03 AM in response to Mortandos
    Level 7 (24,409 points)
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    May 5, 2015 10:03 AM in response to Mortandos

    Do you plan to use the full internal disk for Windows?

  • by Mortandos,

    Mortandos Mortandos May 5, 2015 1:19 PM in response to Loner T
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    May 5, 2015 1:19 PM in response to Loner T

    Yes - unless there is a downside?!

  • by Loner T,

    Loner T Loner T May 5, 2015 1:40 PM in response to Mortandos
    Level 7 (24,409 points)
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    May 5, 2015 1:40 PM in response to Mortandos

    No there is no downside. If you plan to use the entire disk, you should install a small disposable OSX installation (16-32GB) and install Windows on the rest of the disk. The external OSX disk is really not necessary. The advantage is that you can run OSX from the same disk, if there are any issues for Windows recovery.

  • by Mortandos,

    Mortandos Mortandos May 5, 2015 1:48 PM in response to Loner T
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    May 5, 2015 1:48 PM in response to Loner T

    So how do I proceed now since the Boot Camp assistant is giving me this error message: The startup disk cannot be partitioned or restored to a single partition.

  • by Loner T,

    Loner T Loner T May 5, 2015 1:50 PM in response to Mortandos
    Level 7 (24,409 points)
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    May 5, 2015 1:50 PM in response to Mortandos

    Can you post the output of the following Terminal commands?

     

    diskutil list

    diskutil cs list

    sudo gpt -vv -r show /dev/disk0

    sudo fdisk /dev/disk0

     

    The "sudo" commands will prompt for your password, and it will not be echoed back. You may also see a warning about improper use of "sudo" and potential data loss due to "abuse" of the command.

  • by Mortandos,

    Mortandos Mortandos May 5, 2015 2:11 PM in response to Loner T
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    May 5, 2015 2:11 PM in response to Loner T

    /dev/disk0

       #:                       TYPE NAME                    SIZE       IDENTIFIER

       0:      GUID_partition_scheme                        *1.0 TB     disk0

       1:                        EFI NO NAME                 209.7 MB   disk0s1

       2:         Microsoft Reserved                         125.8 MB   disk0s2

       3:       Microsoft Basic Data Windows                 524.3 GB   disk0s3

       4:       Microsoft Basic Data MACINT                  475.6 GB   disk0s4

    /dev/disk1

       #:                       TYPE NAME                    SIZE       IDENTIFIER

       0:      GUID_partition_scheme                        *256.1 GB   disk1

       1:                        EFI EFI                     209.7 MB   disk1s1

       2:                  Apple_HFS MAC SSD                 255.2 GB   disk1s2

       3:                 Apple_Boot Recovery HD             650.0 MB   disk1s3

     

    diskutil cs list

    No CoreStorage logical volume groups found


    sudo gpt -vv -r show /dev/disk0

     

    gpt show: /dev/disk0: mediasize=1000204886016; sectorsize=512; blocks=1953525168

    gpt show: /dev/disk0: PMBR at sector 0

    gpt show: /dev/disk0: Pri GPT at sector 1

    gpt show: /dev/disk0: Sec GPT at sector 1953525167

           start        size  index  contents

               0           1         PMBR

               1           1         Pri GPT header

               2          32         Pri GPT table

              34        2014        

            2048      409600      1  GPT part - C12A7328-F81F-11D2-BA4B-00A0C93EC93B

          411648      245760      2  GPT part - E3C9E316-0B5C-4DB8-817D-F92DF00215AE

          657408  1024000000      3  GPT part - EBD0A0A2-B9E5-4433-87C0-68B6B72699C7

      1024657408   928864256      4  GPT part - EBD0A0A2-B9E5-4433-87C0-68B6B72699C7

      1953521664        3471        

      1953525135          32         Sec GPT table

      1953525167           1         Sec GPT header

    sudo fdisk /dev/disk0

    Disk: /dev/disk0 geometry: 121601/255/63 [1953525168 sectors]

    Signature: 0xAA55

             Starting       Ending

    #: id  cyl  hd sec -  cyl  hd sec [     start -       size]

    ------------------------------------------------------------------------

    1: EE    0   0   2 - 1023 255  63 [         1 - 4294967295] <Unknown ID>

    2: 00    0   0   0 -    0   0   0 [         0 -          0] unused     

    3: 00    0   0   0 -    0   0   0 [         0 -          0] unused     

    4: 00    0   0   0 -    0   0   0 [         0 -          0] unused

  • by Loner T,

    Loner T Loner T May 5, 2015 2:46 PM in response to Mortandos
    Level 7 (24,409 points)
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    May 5, 2015 2:46 PM in response to Mortandos

    BCA is confused between the Startup Disk (SSD) and the 1TB disk. Is there data on the 1TB disk that you want to save? If the whole disk will be used, would you be willing to reformat it as an MBR disk for Windows after you save your data?

  • by Mortandos,

    Mortandos Mortandos May 5, 2015 3:47 PM in response to Loner T
    Level 1 (0 points)
    May 5, 2015 3:47 PM in response to Loner T

    I unlplug(ged) the SSD when using Windows.

     

    There is nothing really important on the 1 TB disk and I would be willing to reformat it as a MBR disk for Windows. Based on this - how would you proceed?

  • by Loner T,

    Loner T Loner T May 5, 2015 4:04 PM in response to Mortandos
    Level 7 (24,409 points)
    Safari
    May 5, 2015 4:04 PM in response to Mortandos

    My suggestion is to create a USB OS X installation on a 16GB flash using OS X: Installing OS X on an external volume - Apple Support. Use this USB to boot, run BCA and format the internal disk as an MBR disk, and install Windows.

  • by Mortandos,

    Mortandos Mortandos May 5, 2015 6:40 PM in response to Loner T
    Level 1 (0 points)
    May 5, 2015 6:40 PM in response to Loner T

    1) Why the USB installation - so that the SSD isn't connected? 2) Does the BCA format the internal drive as a MBR or do I have to do that manually?

  • by Loner T,

    Loner T Loner T May 5, 2015 6:46 PM in response to Mortandos
    Level 7 (24,409 points)
    Safari
    May 5, 2015 6:46 PM in response to Mortandos

    BCA (and Windows installer) get confused when two storage devices which are potential candidates for installation, one external, one internal, are connected. A USB flash device for booting addresses this issue. BCA will create a Hybrid MBR drive. You should format it as MBR before you start BCA.

  • by Mortandos,

    Mortandos Mortandos May 5, 2015 7:06 PM in response to Loner T
    Level 1 (0 points)
    May 5, 2015 7:06 PM in response to Loner T

    Why does it make a difference for BCA whether I boot OS X from a SSD or from a USB? Both are external storage devices.

  • by Loner T,

    Loner T Loner T May 5, 2015 7:37 PM in response to Mortandos
    Level 7 (24,409 points)
    Safari
    May 5, 2015 7:37 PM in response to Mortandos

    There are significant differences, between the two types. If you boot from either device and run diskutil info / and look at differences between the two, it makes it easier to explain.

     

    Here is an example of what problems can be created when using an external and an internal storage - "We couldn't create a new partition or locate an existing one. Form more information, see setup log files".

     

    Please also see Boot Camp: Windows installation boots to black screen with blinking cursor - Apple Support.

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