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I'm using the built-in SD card reader on a Macbook Pro (15", late 2011) running Yosemite, and it treats every SD card as write-protected regardless of the position of the physical switch on the card.

Apparently this is a fairly common problem. I've already tried all the solutions given in this question, with no success. The only thing left that I can think of to try is making physical repairs to the drive. Since this problem is likely caused by a malfunctioning sensor for a setting I don't care about, that seems like overkill if there is a way to do it in software.

Is there any known way to tell the drive or the OS to ignore the write-protection setting and treat a protected SD card as writeable?

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  • buy a can of contact cleaner. 5 quid/bucks/shekels from Maplins/Radio Shack etc. Power down first. – Tetsujin Jan 19 '15 at 19:19
  • @Tetsujin First thing I tried. Problem persists. – Robert Jan 19 '15 at 19:41
  • one SD card, all, or random? – Tetsujin Jan 19 '15 at 19:42
  • All SD cards I've tried. Used to be intermittent, now it's every time. – Robert Jan 19 '15 at 19:53
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    @Tetsujin Reviving this because I see this is a well propagated misconception: It's not the contacts. The SD card lock is a mechanical switch that has no electronic connection to the rest of the card. You can find out for yourself by looking inside a card. It's up to the system to decide to respect the read-only position or not. So this question remains an interesting problem waiting for a solution. – Duvrai Feb 15 '17 at 13:04
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No. You cannot override the write protection status of an SD Card via software.

The read/write status is handled by the firmware of the SD card host controller not by the driver. From Toshiba (manufacturer of these chips):

Content protection can be realized by using the [controller] with firmware.

enter image description here

Inside the SD card reader are a series of pins that get connected if the write protection is enabled. This tells the controller that write protection is enabled (Picture is not of the MacBook connectors, but the best one to illustrate how it works I could find online).

enter image description here

It is most likely that these pins are "stuck" together causing the controller to "see" the card as protected. You can attempt to clean it out or as a better alternative, just purchase an inexpensive USB SD Card Reader.

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I have sacrificed a micro SD to SD adapter in order to see that there is no wire or lever going from the slider to the micro SD card, hence the protection it NOT in the card but in the reader.

enter image description here

Yet it could be possible to overcome the lock with proper software (kind of spoofing or masquerading).

I happen to have a true full size no adapter Sandisk Extreme SD card that cost me more than 60 euros (I won't open it for curiosity). It is almost always read only on my Macs (with either Mac OS or Linux).

Just like it used to be with floppies: cover the hole!

Let me do it. Cover the hole with brown postal packaging tape (opaque and thin), being careful not to cover any electrical pin.

Hole covered

Now my SD card is almost always writable, even if the slider is in lock position, which proves that it does not know the slider position and does not have built-in lock.

After many years and many cards thrown to the bin for nothing...

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  • NO WAY! I spent so much time futzing with the adapter, pushing it in this way, holding it that way. And your method WORKED. I'm in awe – NoethersOneRing Dec 11 '20 at 20:42
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    For history: floppies followed tape cassettes in the locking principle. – Pierre ALBARÈDE Jan 31 at 23:08

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