AMD's New Threadripper Chips Have a Hidden Fuse That Blows When Overclocking

There's even worse possibilities, I think some hardware has ~1KB of executable OTP which can be programmed in that manner - so it may just be possible to implement some kind of backdoor that resides in the physical CPU. Maybe something only a state-level attacker could do.

For example, it could prevent CPU side-channel mitigations from ever working, somehow, e.g. by repeatedly writing to a private internal register to stealthily keep the CPU vulnerable. And few would ever know about it, because it's hidden in an on-chip security processor.

Personally I utterly hate all AMD chips which have a Platform Security Processor. Locking down your own property to prevent you from accessing it should be illegal.

There is a full Trustronic Trusted Execution Environment running in there, on both GPU and CPUs, I believe. For example the TEE firmware blob for a radeon GPU on Linux is "/lib/firmware/amdgpu/psp_13_0_7_sos.bin", with "sos" meaning Secure Operating System. And some of these firmware files are encrypted, so you can't reverse engineer them.

The moment some ARM SoC company such as Rockchip comes up with a chip that's within an order of magnitude in performance, then my AMD chip (EPYC) is going in the bin. After being smashed to pieces with a hammer, live on YouTube, with an explaination why. That might get AMD marketing to pay attention.

Update: Ampere Altra CPUs have seperate power pins for blowing eFuses, you can find it in the public datasheet here[1], on page 55, the supply pins are EFUSE_MFG_VDDQ1P8 and EFUSE_PCP_VDDQ1P8. It says tie to GND if unneeded.

Also they have a public datasheet for the chip. I wonder if we can buy unfused CPUs without secure boot enabled? Or is that the default state of the chip?

Could someone design a simple and cheap open-source motherboard for one of these processors, it's only a matter of time before the chips start turning up on Ebay? We will need more documentation from Ampere than just the datasheet, of course.

1. https://uawartifacts.blob.core.windows.net/upload-files/Altr...

I was an early adopter and got bitten by it via a Lenovo.

this used to be even bigger in the Xeon days. Being able to drop in a $50 upgrade to x99 and get the 2-3 best chip in socket owns actually. X99 isn't bad if you've got a 18-core chip running at 3.8 ghz all-core (with all-core turbo enhancement), and you can address 256GB of memory in a consumer board with dirt-cheap 32GB RDIMM sticks (they are basically under $20 now) since many X99 boards also support RDIMM (including on consumer cpus).

Like let's not cheer literal e-waste here. Secondary users keep hardware out of landfills, a lot of those customers have existing systems they want to upgrade or want to build using whitebox brands like supermicro/asrock rack, the EU absolutely needs to tamp down on this practice.

The most silly part is, how does locking it to the brand do anything anyway? If you locked the CPU to the board then sure, that makes sense, but the threat model here is an employee is stealing your CPUs and swapping them out with something cheaper, and this makes them... find another lenovo or dell branded CPU to match it with? and with PSP allowing secure manipulation of non-volatile storage, there is zero reason to make this a permanent fuse, why shouldn't you allow this to also be unlocked when it's time for disposal? like if you want to prevent the "evil maid" attack you would want it to be both more tightly locked to the board and also unlockable so it can be serviced.

(even if you don't want to trust non-volatile storage, you can also make "pseudo-non-volatile" out of plain old e-fuses. even number of fuses blown = unlocked, odd = locked. being able to lock and unlock say 128 times is plenty, in practice.)

And ironically the e-waste this produces (brand-locked chips) actually makes the cost of these evil-maid swapping attacks even cheaper, because nobody wants them on the secondary market, the cheapest platform-locked naples chips are probably already absolutely worthless because nobody wants naples to begin with, let alone brand-locked naples.

it so very obviously is narrowly targeted at making sure the secondary market is a confusing mess that buyers want to avoid. Creating e-waste to sell more chips. Again, the EU really needs to step in, it is noxious, they should even be forced to release a firmware update unlocking existing chips (AMD is the root of trust and can do this).

Sadly Intel has also really cracked down on xeon secondary sales as well - starting with broadwell, xeons can't be used in consumer Z97 boards, and they went to the same thing on X299, as well as cracking down on unlocked multipliers on certain skus (1660v3 has it, among others) and all-core turbo enhancement with broadwell-EP. It would be nice if you could drop an epyc into your threadripper board, too, that's basically the modern equivalent of ye olde xeon ebay upgrade. On the other hand, there’s no surprises either - socket compatible cpus are socket compatible, your board may only work with consumer chips but it does work with all of them.

And frankly people are also underplaying the fact that AMD does this on consumer socket as well - consumers would benefit from having a bunch of cheap zen2/zen3 chips from old OEM systems in a year or two here, that would push prices down even farther.

There is also a general danger that if the systems don’t have any resale value anymore that they will be scrapped entirely instead of resold as either parts or a complete server. If the value of the server is nothing, nobody will bother re-using it. You’ve literally turned working parts into e-waste, nobody wants them anymore and it stops being economically viable to bother for the handful of people who do. Everyone benefits from reduced friction in a market.