This question has already been asked here before, but I feel I'm missing something or don't understand something from the answers.

I have a MacBook Air - very little space left. I have a 128GB SD card. I want to dual boot Windows 7 and OSx. The Windows 7 would run from the SD card.

I've prepared a USB drive with the Windows installation through Bootcamp assistant successfully, but then the "Install or remove Windows 7" checkbox is greyed out. It also gives me "You must have at least 50 GB of space available" message, but I want to install it on the SD card.

Does bootcamp not support writing on SD cards? Is there a workaround?

  • Whether or not Boot Camp Assistant allows processing an SD Card to install Windows on I can't say as I don't have a spare SD Card to test with. If Boot Camp Assistant doesn't recognize the SD Card as an acceptable location to install, nonetheless that doesn't stop you from booting the Mac via the USB installer and attempting to install Windows to the SD Card. That said, you may have some issues where as you'll have to option boot selecting Windows after the install and going forward. Again If I had a spare SD Card I'd test it for you, but I don't. Continued in next comment... Commented Jul 24, 2016 at 14:36
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    I do have an SD Card that I have installed OS X to with my base minimum configuration to use in an emergency and what I will tell you is, even though I have a very high end and fast SD Card, IMO it's not fast enough for normal everyday use. YMMV. Commented Jul 24, 2016 at 14:36
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    If you were to get this to work, it would be horribly slow. An SD card will max out at 150KB/s whereas a USB 2.0 480MB/s and SATA is 3GB/s. This would be painful
    – Allan
    Commented Jul 24, 2016 at 15:06
  • Could you make it work with SD? Commented Jul 23, 2017 at 0:20

1 Answer 1


One question posted at Ask Different deals with running Windows from a external drive. While the questions deals with Windows 10, the answer seems to indicate a BIOS boot method is used. Therefore, the answer might be adapted to work with Windows 7. Below is a link to this question.

Is it possible to use Boot Camp with Windows 10 from an external HDD?

In your case, the problem really is not whether you can get the software to work, but rather the hardware media you are choosing. For a while now, Microsoft has had the ability to run Windows from a flash drive. This is referred to as Windows To Go. If you read the link, you will realize this requires the use of special flash drives design to endure the large amount of reads/writes required by the Windows operating system. A normal SD card probably would not survive long under such conditions.

  • FWIW If you're going to install Windows 7 to a separate Drive/SD Card on a Mac, like a Mac Pro or other type Mac using an SD Card, I'd opt for using GPT vs (hybrid) MBR. Commented Jul 24, 2016 at 14:57
  • @ user3439894: You can not install Windows 7 using a EFI boot method on any Mac computer. Therefore, you must use a hybrid GPT partitioning scheme. Note that starting in 2015, Apple removed the BIOS boot method which is why you can not install Windows 7 on most (if not all) 2015 and later Macs. Commented Jul 24, 2016 at 15:15
  • Thanks for the info! Let me say, I'm glad I switched to Mac 10 years ago and have absolutely no need whatsoever to run Windows natively on my Mac. I did for the first year I switched and then removed it, as I have no regular need for it. I do keep a Windows virtual machine for the rare instances I might need it. Personally I'd never go back to Windows and would run Linux if I didn't have Mac. :) Commented Jul 24, 2016 at 15:25

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