Fusing the JTAG port

One thing has really been dwelling on my conscience since I interviewed with a certain mobile device manufacturer. They disclosed something to me which could very well be common practice for a large part of the industry, but really shouldn't be.

For those unfamiliar with JTAG, it's a programming / testing methodology for highly integrated circuits and chips on a circuitboard. Essentially, JTAG is a software-controllable circuit probing method that goes where hands cannot. Manufacturers have used it for a long time to mass-program their mobile devices. All of phone's firmware can be programmed at once through this interface, even if that firmware lives on multiple chips.

However, some chip and mobile device manufacturers have taken it upon themselves to actually fuse the JTAG port, so that once it's been programmed, that interface can be burned - made permanently, electrically disconnected. While this is good on some levels for security purposes, it has the awful side-effect that the device can never be re-used or refurbished. When a device can never be reused or refurbished, it often ends up in the scrap heap, just like billions of other mobile phones.

Aside from restricting the owner's freedom to do as he or she whishes with the mobile device, the Free Software Foundation would also term such manufacturing practices as 'defective by design'.

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