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

It should be on disk0s1. Can you mount disk0s1?

Look at man nvram and the example section. The first one on Yosemite says

example% nvram boot-args="-s rd=*hd:10"

 

       Set the boot-args variable to "-s rd=*hd:10".  This would specify single user mode with the root  device  in  hard

       drive partition 10.

The description does not explicitly say what rd is but rd is the root device based on the following part. You can specify the rd to be any partition which is visible on a connected disk. In your case it should be partition 1. You can run this command with your OS X connected and point to "*hd:1", reboot and disconnect the external OS X disk and see if it will boot from the dd'ed ISO image.

In my case, if the DU process completes, I can just power cycle, and hold the Alt key and I can boot from the ISO image on the internal drive. The other option is to use Rufus USB or diskpart to build a USB to boot from.

If you shutdown your Mac, disconnect your external OSX disk and power up your Mac and hold Alt/Option key, do you see a bootable entry called Windows or EFI Boot?

Are there any visible files in the the disk0s1 directory? The file system should be ISO or CDFS, it shows as Windows_NTFS.

You can boot from either MBR or GPT. For example, on MacPro machines, where you have more than one disk drive, the Windows drive can be formatted as MBR, and the Windows installation is NTFS. You cannot boot OS X from MBR, but you can boot Windows from MBR disks.

You do not need to format the small 10GB partition. It can be free space and can be at the end of the disk. DD should make it the same format as the source since you are overwriting it anyway.

If you are planning to copy files, I suggest making it exFAT. If you have Tuxera, make it NTFS.

So far I have tested this on a 2008 MBA running SL 10.6.8 (I do not have any other available machine till I can get a 2010 MBP for testing).

1. Disk is GPT.

2. Create a 4GB exFAT partition.

3. Copy the contents of W7 ISO to this partition. The installer should not have files larger than 2GB.

4. Use Fdisk to make this partition bootable.

5. Use bless

     sudo /usr/sbin/bless --verbose --device /dev/disk0s3 --setBoot --legacy --nextonly

6. Restart (first time I had no bootable device which was corrected with steps 4 and 5).

I have done a couple of SMC Reset and NVRAM resets to diagnose what is going on. Using the NVRAM command works, but I want to try and get it to the normal BC behavior as much as possible.

If I make further progress (rather unlikely), I will post an update.

Here is output of the bless command.

sudo bless --verbose --device /dev/disk0s3 --setboot --nextonly --legacy

Password:

EFI found at IODeviceTree:/efi

Firmware feature mask: 0xC0003FFF

Firmware features: 0xC0003513

Legacy mode suppported

Got IODeviceTree:/rom

Got start address ffc00000

Got size 390000

Found ATA interconnect in protocol characteristics

IOGUIDPartitionScheme

OWC Drive OWC Drive

  IOBlockStorageDriver

   IOATABlockStorageDevice

    AppleATADiskDriver

     ATADeviceNub

      AppleIntelPIIXPATA

       PRID

        AppleIntelPIIXATARoot

         PATA

          AppleACPIPCI

           PCI0

            AppleACPIPlatformExpert

             MacBookAir1,1

              Root

Setting EFI NVRAM:

  efi-boot-next='<array><dict><key>MemoryType</key><integer size="32">0xb</integer><key>StartingAddress</key><integer size="64">0xffc00000</integer><key>IOEFIDevicePathType</key><string>HardwareMem oryMapped</string><key>EndingAddress</key><integer size="64">0xfff8ffff</integer></dict><dict><key>IOEFIDevicePathType</key><strin g>MediaFirmwareVolumeFilePath</string><key>Guid</key><string>2B0585EB-D8B8-49A9- 8B8C-E21B01AEF2B7</string></dict><dict><key>IOEFIBootOption</key><string>HD</str ing></dict></array>'

Setting EFI NVRAM:

  IONVRAM-DELETE-PROPERTY='efi-boot-file'

Setting EFI NVRAM:

  IONVRAM-DELETE-PROPERTY='efi-boot-mkext'

NVRAM variable "boot-args" not set.

Check the output of sudo fdisk /dev/disk0 . Post the output and i can give you more specific steps.

If there is an entry for disk0s2 (using the start/size from the gpt command), then mark it as bootable using flag command.

Here is an example on my MBP which has a GPT/Hybrid MBR.

sudo gpt -vv -r show /dev/disk0

Password:

gpt show: /dev/disk0: mediasize=256060514304; sectorsize=512; blocks=500118192

gpt show: /dev/disk0: Suspicious MBR at sector 0

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

gpt show: /dev/disk0: Sec GPT at sector 500118191

      start       size  index  contents

          0          1         MBR

          1          1         Pri GPT header

          2         32         Pri GPT table

         34          6        

         40     409600      1  GPT part - C12A7328-F81F-11D2-BA4B-00A0C93EC93B

     409640  250392096      2  GPT part - 53746F72-6167-11AA-AA11-00306543ECAC

  250801736    1269536      3  GPT part - 426F6F74-0000-11AA-AA11-00306543ECAC

  252071272        664        

  252071936  248045568      4  GPT part - EBD0A0A2-B9E5-4433-87C0-68B6B72699C7

  500117504        655        

  500118159         32         Sec GPT table

  500118191          1         Sec GPT header

 

$ sudo fdisk /dev/disk0

Disk: /dev/disk0 geometry: 31130/255/63 [500118192 sectors]

Signature: 0xAA55

         Starting       Ending

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

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

1: EE 1023 254  63 - 1023 254  63 [         1 -     409639] <Unknown ID>

2: AC 1023 254  63 - 1023 254  63 [    409640 -  250392096] <Unknown ID>

3: AB 1023 254  63 - 1023 254  63 [ 250801736 -    1269536] Darwin Boot

*4: 07 1023 254  63 - 1023 254  63 [ 252071936 -  248045568] HPFS/QNX/AUX