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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

Mortandos Author

Level 1

4 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.

Loner T

Level 9

59,483 points

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?

Mortandos Author

Level 1

4 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".

Loner T

Level 9

59,483 points

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?

Mortandos Author

Level 1

4 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

Loner T

Level 9

59,483 points

Jun 4, 2015 11:30 AM in response to Mortandos

Does diskutil list show it?

Mortandos Author

Level 1

4 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

Loner T

Level 9

59,483 points

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

Mortandos Author

Level 1

4 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?

Loner T

Level 9

59,483 points

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 .

Mortandos Author

Level 1

4 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

Select a disk in the sidebar, then click Restore.
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.
Drag the disk that will hold the contents of the disk image to the Destination field.
Click the Restore button.