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

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Level 1

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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

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Answer 1

Loner T

Level 9

59,471 points

May 3, 2015 4:25 PM in response to Mortandos

What does this screen show on your iMac?

Please also see Will Windows 7 Pro run with 16GB of Ram in Macbook Pro Early 2011 13-inch?.

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Answer 2

Mortandos Author

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May 3, 2015 5:01 PM in response to Loner T

@Loner T, it looks like yours except my processor is different and it says "Pro" after Windows 8.1 and the restriction: Installed memory (RAM) 16.0 GB (2.48 GB usable). The system type is identical, 64-bit so it's not the 32-bit limitation (I read about that).

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Answer 3

Loner T

Level 9

59,471 points

May 3, 2015 5:14 PM in response to Mortandos

Can you check msconfig in Windows as shown in the linked discussion?

You may also want to look at https://msdn.microsoft.com/en-us/library/windows/desktop/aa366796%28v=vs.85%29.a spx?f=255&MSPPError=-2147217396.

What is the year/model of your iMac (my guess is a 2011 iMac)? Can you post the output of the highlighted command from OS X Terminal?

sysctl hw.cpu64bit_capable

hw.cpu64bit_capable: 1

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Answer 4

Mortandos Author

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May 3, 2015 6:10 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.

The result of the command is hw.cpu64bit_capable: 1

I'm not sure what I'm looking for when executing the msconfig command in Windows.

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Answer 5

Loner T

Level 9

59,471 points

May 3, 2015 6:22 PM in response to Mortandos

You should take a look at MsConfig -> Boot -> Advanced Options and look at the highlighted part.

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Answer 6

Mortandos Author

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May 3, 2015 7:37 PM in response to Loner T

That part is like in your picture, unchecked and with a zero. I changed it, checked the box and set it to 16 GB, applied it and restarted and there was no change (showing the system configuration). However, running msconfig again showed zero and and the box unchecked (again).

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Answer 7

Loner T

Level 9

59,471 points

May 4, 2015 5:19 AM in response to Mortandos

Can you test after

SMC Reset - Resetting the System Management Controller (SMC) on your Mac - Apple Support

NVRAM Reset - How to Reset NVRAM on your Mac - Apple Support

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Answer 8

Mortandos Author

Level 1

4 points

May 4, 2015 2:18 PM in response to Loner T

I did both following the provided instructions but nothing has changed. Isn't it strange that when I use MSCONFIG as you suggested and then check MAXIMUM MEMORY and choose 16384 and then click ok and then immediately check again it's back to "0" ?

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Answer 9

Loner T

Level 9

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May 4, 2015 2:25 PM in response to Mortandos

Are you using an account on Windows which has Administrative Rights?

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Answer 10

Mortandos Author

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May 4, 2015 2:40 PM in response to Loner T

Yes, there is only one account and I checked, it shows my name, email address and then the word ADMINISTRATOR.

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Answer 11

Loner T

Level 9

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May 4, 2015 5:43 PM in response to Mortandos

Is this a new installation of Windows?

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Answer 12

Mortandos Author

Level 1

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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.

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Answer 13

Loner T

Level 9

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May 4, 2015 7:43 PM in response to Mortandos

1. What is the year/model of your iMac?

2. Was Windows installed using EFI Boot?

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Answer 14

Mortandos Author

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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.

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Answer 15

Loner T

Level 9

59,471 points

May 4, 2015 8:04 PM in response to Mortandos

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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