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

Top-ranking reply

Loner T

Level 9

59,536 points

Posted on May 4, 2015 8:04 PM

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.

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195 replies

Mortandos Author

Level 1

4 points

May 21, 2015 4:14 PM in response to Mortandos

Is there any way to mirror / copy a working VM Parallels Desktop virtual disk (Windows) to my internal Hard Drive (since I can use that completely for Windows because I boot Yosemite from my external SSD)?

Loner T

Level 9

59,536 points

May 21, 2015 5:43 PM in response to Mortandos

A VM (using any virtualization) does not need BCA and hence there are no restrictions for the installation. You can install Windows using a VM engine from an ISO of Windows.

Can I suggest a test for you SuperDrive? Temporarily set you System Date to sometime in 2007-2008 and test your SuperDrive again?

Mortandos Author

Level 1

4 points

May 21, 2015 6:17 PM in response to Loner T

changing the date didn't help. You meant just change it and then try so not reboot again?!

Regarding the VM - I might not have explained it right, I have Parallels Desktop with an existing Windows VM and I was wondering whether I can copy / mirror / convert it to my internal hard disk and then boot from it (simply because of performance reasons assuming that Boot Camp is faster than Parallels.

Loner T

Level 9

59,536 points

May 21, 2015 6:26 PM in response to Mortandos

If you change the date, please ensure you are not syncing time with an external NTP server. Reboot is fine. Check your system date, it should be in 2007-2008.

There is no method to convert a VM Virtual Disk to a Bootcamp Partition. However, if you use Windows Backup/Restore and back up your Windows VM installation, and install Bootcamp Windows, you can try a restore of your Windows backup to the BC Partition. In your case, you are unable to install Windows in the first place due to your Optical drive issue.

Loner T

Level 9

59,536 points

May 26, 2015 2:12 PM in response to Mortandos

Yes. After you install Windows on Macbook, you can use a third-party tool like Winclone (or CampTune) and backup the Windows image, 'generalize' it (it will remove the Macbook-specific BC drivers) and then restore it to the iMac. Once it iw working on your iMac, it can be removed using BCA from the Macbook.

To use Winclone, you can look at https://twocanoes.zendesk.com/hc/en-us/articles/203444057-Boot-Camp-Migration-Ov erview.

Loner T

Level 9

59,536 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

59,536 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

59,536 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

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.

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

59,536 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 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

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

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