7

I heard in a recent presentation that the XBox 360 uses an eFuse to prevent users from reverting back to prior boot/firmware image. What is an eFuse and how do they work?

tyblu
  • 8,167
  • 6
  • 40
  • 70
Scott
  • 387
  • 2
  • 6
  • 9

2 Answers2

9

It's an irreversible part of the chip which is "burnt" out (without causing damage to the rest of the chip) and is usually a single configuration bit. The bit (and subsequent bits) might control something like software version, or whether the Xbox supports 1080p, or whether you can play certain region discs... Pretty much anything you can imagine. Like a one time programmable read only memory. They are a concern because it effectively allows a manufacturer to obsolete a product remotely without any consent from the owner.

That's the paranoid view, anyway.

Thomas O
  • 31,546
  • 57
  • 182
  • 320
  • The non-paranoid view says that if a company like Microsoft started intentionally "breaking" xboxs, there would be a lot of backlash and lawsuits. They do have the right to prevent someone from modifying (aka hacking) the system and putting non-authorized code on the system. – Kellenjb Dec 30 '10 at 21:47
  • 1
    @Kellenjb, I don't like it either way - If I buy hardware, it belongs to ME, and not the company I bought it from. I can do whatever I like with it, as long as it's not actually illegal. (And even then, Microsoft shouldn't be involved.) – Thomas O Dec 30 '10 at 22:30
  • @Thomas O Sure, you own the hardware, but you don't own the software or firmware, instead you just own a license to use it. If you don't like the terms of the license then don't buy it, end of story. – Kellenjb Dec 30 '10 at 22:39
  • 1
    @kellenjb, Yeah, that's where software licensing gets a bit dodgy... I mean, if you hack it to run homebrew games by physically modifying the hardware, have you invalidated the EULA, which really only applies to software/firmware? – Thomas O Dec 30 '10 at 23:19
  • @Thomas O, no, not in the USA (hardware only) anyways that was established in law quite some time ago. However it continues to be illegal(hardware AND software) in Australia and I believe parts of Europe. Of cause in Asia anything goes(hardware/software), which is probably why alot of the hack kits are made there. You example is generally the accepted one; i.e. homebrew/streaming is ok, but no licensed games or modification of firmware OS. – Anonymous Type Dec 31 '10 at 01:06
  • It is also worth remembering that Microsoft sells their hardware for a loss because they know they can make up the cost in media sales. If they left it as a completely open system we all would end up having to pay more up front. – Kellenjb Dec 31 '10 at 18:59
  • @kellenjb. That's their business decision, but they aren't allowed to force me to do that, because I bought their hardware (actually, I got a Wii instead because I was sick of both Sony + Microsoft's crappy reliability, but that's beside the point...) – Thomas O Dec 31 '10 at 19:23
  • @Thomas O Can you provide me some sources that say they aren't allowed to force you to do that once you buy from them? – Kellenjb Dec 31 '10 at 20:16
  • 1
    @kellenjb. I'm not sure if they are or are not, but either way, I think, personally, it's wrong, because it's my hardware. If I own it personally the company can't take it off of me or change it without my permission. It's akin to a car manufacturer saying you can only drive their cars on roads that they own, or if you tweak the engine to make it go faster, you have to pay them the money they would get for the higher-end model with the faster engine. I just don't like it. – Thomas O Dec 31 '10 at 20:34
  • Thomas O, your description of an "eFuse" sounds no different than the "fuse bits" in many MCUs and programmable array logic chips and some FPGA chips. So is an "eFuse" identical to a fuse bit, or is there some difference I"m missing? – davidcary Jan 02 '11 at 06:06
  • @davidcary there are similarities, but I think an eFuse can be changed from software, whereas an MCU fuse can be changed only from a programmer. Also, MCU fuses are often EEPROM or FLASH, so they can be reset. – Thomas O Jan 02 '11 at 11:26
4

According to Wikipedia

In computing, eFUSE is a technology invented by IBM which allows for the dynamic real-time reprogramming of computer chips. Speaking abstractly, computer logic is generally 'etched' or 'hard-coded' onto a chip and cannot be changed after the chip has finished being manufactured. By utilizing an eFUSE (or more realistically, a number of individual eFUSEs), a chip manufacturer can allow for the circuits on a chip to change while it is in operation.

stevenvh
  • 145,145
  • 21
  • 455
  • 667
  • Thank you for the comment. This just tells us what an eFuse accomplishes. That is " utilizing an eFUSE... a chip manufacturer can allow for the circuits on a chip to change while it is in operation". – Scott Dec 30 '10 at 18:55
  • To my untrained (relatively) mind, this looks suspiciously like a low complexity FPGA... – Sushrut J Mair Dec 31 '10 at 13:00