No sound on 27 inch iMac Mid 2011 running Windows 8.1 on Botcamp

Does your built-in Optical drive function properly?

amytom12 wrote:

And oh, I forgot to mention. When I was installing Windows 8.1, I got a MBR table error and something about EFI's and GPT. I looked on YouTube and this guy said to go to terminal on my mac side and put some codes in. I don't know if this effects the sound.

Yes, it does. If you do not use the internal Optical drive and a DVD (or CD) to install Windows on your specific model and instead use a USB (or manually choose) EFI boot, the Audio devices are not exposed correctly. This is indicated by the current BIOS Mode being UEFI. On your specific 2011 model, it should be Legacy (or BIOS).

The only method to switch to BIOS mode, is to remove the current installation using Remove Windows from your Mac - Apple Support and then use a DVD in the Optical drive to install W8.1. The 'code' you were asked to input in Terminal removed the MBR, forcing a UEFI installation, and causing the Audio to malfunction.

You do not need W10 to get sound out of your 2011 iMac. W7/W8.1 work very well. Can you check the setting of BIOS Mode if you run msinfo32 from the Start -> Run command? If it is 'UEFI', your sound will not work. You need to ensure your Windows is installed using legacy BIOS mode, which is the BC Assistant default for your model.

What is the macOS version on your iMac? High Sierra has some issues in this area.

download apples bootcamp driver zip

Boot Camp Support Software 5.1.5640

and install the audio driver for the audio chipset / I recall it being cirrus logic

Install GPT Fdisk (aka gdisk) from GPT fdisk download | SourceForge.net. If you are on High Sierra, you will also need to disable SIP by booting in Local Recovery (Command+R) and running

csrutil status

csrutil disable

csrutil status

If it shows 'disabled', boot normally and rebuild MBR to match the new GPT information thus resetting the Hybrid MBR. Use defaults for other questions (like partition codes). The only values that need modifications are the Boot flags and step 10. Accept all other defaults that Gdisk offers. Please see thesample Q&A as an example. These steps can be repeated if you make a mistake before you get to Step 12, otherwise start from Step 1 for these steps. Step 6 has numbers which are typed with a space between the numbers. Please see the sample Q&A before you execute these steps.

1. Sudo gdisk /dev/rdisk0
2. P (Print list of parts)
3. R (Recover)
4. O (print current Hybrid MBR)
5. H (chooses Hybrid)
6. Partitions numbers to be hybridized: 2 3 4
7. Y (Good for GRUB question)
8. N (part 2 boot flag)
9. N (part 3 boot flag)
10. Y (part 4 boot flag make NTFS bootable partition)
11. O (print current Hybrid MBR)
12. W (Write the new MBR)
13. Y (Yes! write the new MBR)
14. Reboot

Here is sample Q&A for this section. Please notice the Press Enter/Return.

Place EFI GPT (0xEE) partition first in MBR (good for GRUB)? (Y/N): Y

Creating entry for GPT partition #2 (MBR partition #2)

Enter an MBR hex code (default AF): Press Enter/Return

Set the bootable flag? (Y/N): N

Creating entry for GPT partition #3 (MBR partition #3)

Enter an MBR hex code (default AB): Press Enter/Return

Set the bootable flag? (Y/N): N

Creating entry for GPT partition #4 (MBR partition #4)

Enter an MBR hex code (default 07): Press Enter/Return

Set the bootable flag? (Y/N): Y

Do you have the USB flash drive on which you downloaded the W8.1 drivers? If you did not, you can download it from Boot Camp Support Software 5.1.5621 on the Windows and run setup.exe from the Bootcamp folder.

Post the output of the Get Info command, without your Name (replace it with XXXXXX), and I can give you the exact commands to type in Terminal.

With the DVD in the drive, can you post the output of

diskutil list

Let us verify the DVD.

Can you post the output of

diskutil list

Do not use the first option - Create. Your Mac only properly supports Download and Install.

Download will not provide the correct drivers. You will need to find the appropriate drivers from Install Windows 7 on your Mac using Boot Camp - Apple Support for your specific model.

The only useful option is the Install, and using a DVD, not a USB.

amytom12 wrote:

Ok this is what I got when I did " ls -lg (File Path)

iMac:~ XXXXXX$ ls -lg /Users/XXXXXX/Desktop/Win8.1_English_x64.iso

-rw-rw-rw-@ 1 staff
4320526336 Jul 21 19:50 /Users/XXXXXX/Desktop/Win8.1_English_x64.iso

iMac:~ XXXXXX$

So yeah, it does work successfully. Sorry for the inconvenience. 😕

Now run

openssl md5 /Users/XXXXXX/Desktop/Win8.1_English_x64.iso

Your MD5 is correct. Disconnect all external storage. Can you run a SMC and NVRAM Reset?

How to reset the System Management Controller (SMC) on your Mac - Apple Support

How to reset NVRAM on your Mac - Apple Support

Now insert your DVD and run BCA and click on the Install option.

Check the output of

csrutil status

If it is disabled, then run

sudo gdisk /dev/disk0

and continue with the commands as shown. Use defaults as indicated. Once completed, post the output of

sudo gpt -vv -r show /dev/disk0

sudo fdisk /dev/disk0

You need to wait for partitioning to be complete.

Then you need to enter the commands in GDisk as shown in Re: No sound on 27 inch iMac Mid 2011 running Windows 8.1 on Botcamp as shown on page 7 of this discussion.

Once these two steps are complete, then you need to post the output of each of the following commands.

sudo gpt -vv -r show /dev/disk0

sudo fdisk /dev/disk0

Is there a way for you to restore the unmodified Bootcamp Info.plist?

Then your original Bootcamp Info.plist is not in use.