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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

59,483 points

May 28, 2015 4:27 AM in response to Mortandos

On the other Mac, Windows needs to be installed using BC Assistant. Once it is installed, a backup via a cloning tool will allow it to be moved. BCA will not allow Windows to be installed on an external disk. It will have to be done using the internal disk.

Mortandos Author

Level 1

4 points

May 28, 2015 9:26 AM in response to Loner T

No, I mean I CANNOT USE his Macbook. He has an external DVD drive, I have an original Windows DVD, I couldn't use it in my MAC because my superdrive doesn't work, can I use his external DVD drive to boot my Windows DVD directly?

Loner T

Level 9

59,483 points

May 28, 2015 9:47 AM in response to Mortandos

You cannot use BCA to install Windows because it forces the NVRAM on the iMac to point to the internal Optical Drive.

1. Is it possible to take the external Optical drive, extract the drive from the enclosure, and put in to the iMac temporarily?

2. You can also test, letting BCA partition the internal drive, let it fail, and then connect the external drive and use Alt/Option ket to boot from the external Optical drive and point it to this internal disk partition to install Windows.

3. Another option is to copy the entire contents of the Windows installer from the external DVD to the internal Bootcamp partition and select it to boot from.

Mortandos Author

Level 1

4 points

May 28, 2015 10:07 AM in response to Loner T

Option 1 is not an option since it's not my drive and he's very particular with his stuff.

Option 2 doesn't work since BCA doesn't allow me (for whatever reason) to partition the internal drive.

Option 3 sounds good, since I have to format / partition the internal drive manually - how would you partition / format it? Like I mentioned in previous posts I could use the whole internal drive for Windows, so would it be FAT or exFat? Eventually I would like NFTS of course.

Loner T

Level 9

59,483 points

May 28, 2015 10:34 AM in response to Mortandos

You had posted a GPT output with two disks connected. Can you disconnect all external storage and post the output of the same commands for the internal disk?

Mortandos Author

Level 1

4 points

May 28, 2015 10:55 AM in response to Loner T

As soon as I disconnect the SSD the MAC freezes.

Loner T

Level 9

59,483 points

May 28, 2015 11:00 AM in response to Mortandos

Because your only working OS is on the SSD. 👿

Do you have any information on disk0 that you want to save?

Mortandos Author

Level 1

4 points

May 28, 2015 11:15 AM in response to Loner T

Yeah, I figured that it might not be smart to disconnect it, sorry. The internal drive is a regular 1 TB drive that comes with the MAC.

Loner T

Level 9

59,483 points

May 28, 2015 11:18 AM in response to Mortandos

If you do not have any information to save on disk0, can you boot from the external drive and format the internal drive to a FAT32 MBR disk and copy the contents of the Windows installer to this new FAT partition?

Mortandos Author

Level 1

4 points

May 28, 2015 11:28 AM in response to Loner T

I tried that (thought that's what you meant earlier) but because of the FAT32 limitation it doesn't work, one installation file must be too big, I'll get an error that's why I was asking about exFat

Loner T

Level 9

59,483 points

May 28, 2015 11:32 AM in response to Mortandos

You can try exFAT.

Mortandos Author

Level 1

4 points

Jun 3, 2015 10:30 AM in response to Loner T

So I finally had some time to try that, it didn't work. The installer was on a small partition, I could boot from there (but again with EFI which caused me all the problems in the first place?!) but then I couldn't install Windows because it didn't like the MBR but was asking for the GUID.