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 4, 2015 7:25 PM in response to Loner T

Yes, absolutely new. Any thoughts on the msconfig thing? I also was googling around for a solution for my sound problem (it seems that other people also have the code 10 error in the High Definition Audio Controller) but so far nothing has helped me solving this issue.

Mortandos Author

Level 1

4 points

May 4, 2015 7:50 PM in response to Loner T

My Mac: iMac (27-inch, Mid 2011), 3.4 GHz Intel Core i7, 16 GB 1333 MHz DDR3, AMD Radeon HD 6970M 2048 MB.

Yes, I used EFI Boot, I installed it from a USB stick since my superdrive doesn't read DVD's anymore. I used a lens cleaning disc but it didn't help. Also there is dust under the glass of the screen, I really got one of those iMacs with many issues. But in Mountain Lion and Yosemite I never had any other problems and I never really missed the superdrive.

Mortandos Author

Level 1

4 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?

Loner T

Level 9

59,536 points

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.

Mortandos Author

Level 1

4 points

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

Loner T

Level 9

59,536 points

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.

Loner T

Level 9

59,536 points

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.

Mortandos Author

Level 1

4 points

May 6, 2015 7:13 PM in response to Loner T

Ok, that doesn't work so well. I put Yosemite on the USB stick, I booted from the stick, I formatted the hard drive (FAT 32 & MBR) and then I started the Boot Camp Assistant. Of course it doesn't allow me to create a Windows Boot Installer since I have a superdrive, I have to modify the plist again but I cannot choose the INSTALL WINDOWS option, it's grey (the one that formats and partitions the HD from the BCA).

Loner T

Level 9

59,536 points

May 6, 2015 7:57 PM in response to Mortandos

1. If you have OS X on a USB, you will be safer disconnecting the external SSD.

2. You need to run SMC reset and NVRAM reset, because your NVRAM was told by BCA that a Windows installer requiring multiple boots will take over.

3. Since you have OS X on USB, you can leave the internal HDD as a GPT disk, but BCA can be told to partition as Windows by telling it to make Windows 1TB. It will become a Hybrid MBR disk, which is the standard method for Windows on iMacs.

Mortandos Author

Level 1

4 points

May 6, 2015 8:51 PM in response to Loner T

The most importamt thimg right now is to get my MACOS back, the SSDdrive still doesn't show to boot from after the 2 resets. my mac keeps rebooting, i see the apple symbol and then some lines show up, bsd process name corresponding, MACOS version not set yet

Mortandos Author

Level 1

4 points

May 7, 2015 9:14 AM in response to Loner T

Yeah, I had to use recovery and use my Time Machine backup. Quite disturbing, lol. Back to the original problem: BCA didn't allow me to do anything but download the support drivers for Windows, the create Windows installation didn't show (because I have a super drive) and the option to format was grey / not selectable.

Mortandos Author

Level 1

4 points

May 7, 2015 4:45 PM in response to Loner T

This method requires boot camp again (if you're talking about Kunu's solution in this discussion thread) which seems to cause problems on my MAC. And didn't you say that I need to natively boot the Windows installation stick? I'm confused now.

Mortandos Author

Level 1

4 points

May 7, 2015 8:04 PM in response to Loner T

I used the USB to boot and install Windows before. You mean it's possible but not using the BIOS mode but EFU mode or am I getting this wrong? (I'm really new to the MAC as you might have figured by now but I really appreciate your help and much more your patience).

Mortandos Author

Level 1

4 points

May 8, 2015 7:50 AM in response to Loner T

I was actually following this guide:

http://mihail.stoynov.com/2013/04/22/force-boot-camp-into-using-an-iso-image-of- windows-to-create-the-usb-flash-drive-fo…

And then this "manual" method of formatting and installing:

http://www.reddit.com/r/mac/comments/2fy3be/by_popular_demand_my_better_than_boo tcamp_guide/

Which worked well except for the 2.48 GB and the sound issue.

Mortandos Author

Level 1

4 points

May 14, 2015 5:50 PM in response to Loner T

I'm still at at square 1, you suggested I should follow solution number 2 on page 2 of this discussion thread (which would be Kudus solution, Bootcamp without Optical disc drive) but this is not possible since my BCA doesn't allow me to do STEP 5 since I have an optical drive (like I said earlier, I can modify one file so that then it will eventually allow me to do so).

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