It’s not known to be a backdoor, but it’s a juicy attack surface that customers are largely ignorant of and provides little consumer benefit. If I were an NSA employee and my boss handed me a blank check to develop a preboot exploit for Intel PCs, I’d start with IME.
Sometimes EDID eeproms are writable from i2c-dev… And sometimes VRM configuration ports too…
20 years ago the pocketable digital cameras that took over the consumer market didn’t have hot shoes. 30 years ago the compact point and shoot viewfinders that were the weapon of choice for vacationing didn’t have hot shoes. Today neither are relevant and are all outclassed by smartphones, and there is hardly a consumer camera market.
You don’t have to spend five figures for that exposure, but it’s going to be an intentional hobby.
The intersection of people who aren’t five figures into photography and know what a hot shoe is, and people who recognize a wall mount phone trend old.
On Mint Frosting Mobile
Correct. We’ve replaced all our incandescent bulbs except for two 60w contractor bulbs in the a hallway that were installed when the house was built 18 years ago. All of the original higher wattage incandescents died within the first couple of years.
The C64 had a notoriously garbage power supply that would eventually cook the machine regardless of how clean your line power is.
A large green pushbutton with a Molly guard labeled “OK” I found in a scrap pile behind the physics building.
Olivia channeling Bell is the series’ crowning achievement.
Nonfiction oldies that still hold up: The Cuckoo’s Egg by Clifford Stoll and The Soul of a New Machine by Tracy Kidder.
Oh, like back in the Before Times when everything was statically linked?
He’s just trying to get to the Wormhole X-treme™ back to Arrakis
ftfy
But don’t take my word for it.
Clbuttic.
If you ever have the chance to use an old Apple II computer, run a text mode program, wait til the owner is looking in the other direction and turn the power off and back on quickly.
For about a second, before you hear the loud BOOP and the screen clears, you’ll see whatever was on the screen just before you powered it off. But a few characters will be corrupted. Try it again, and wait a half a second longer than before. More characters will be corrupted.
For that brief second you’re looking at the contents of the video RAM, then the ROM (Apple called what we call BIOS now “ROM”) clears the contents and puts up the familiar text banner. The longer the power stays off, the more the contents of those RAM cells decay, and any bit flip will show up as a different character at the corresponding location on the screen.
On a side note, there was an article in the early '80s in Circuit Cellar by Steve Ciarcia showing how you could make a rudimentary digital camera by prying the top off a DRAM chip (some were ceramic with metal lids, or just metal cans) and adding a CCTV camera lens at the right distance. Light can deplete the charge in DRAM cells even faster, and by writing all 1s to the memory, exposing it to light, and reading back the contents, you could get a black and white image of whatever’s shining on the chip.
Modern RAM just needs to be told to refresh. The device itself will go through the refreshing process. But the whole array needs to be refreshed, there’s no LRU scheme to tell what bank or row was last accessed.
Starting with DDR3 it’s not so easy. Density is so high that reading or writing one row affects cells in adjacent rows. Partial target row refresh (PTRR) counters this, where any access of a row is followed by a refresh of adjacent rows. Flaws in this process in early DDR3 controllers was at the heart of rowhammer exploits, where repeated accesses to a memory location could work out what’s stored in physically adjacent memory, even if it’s not privileged. IIRC DDR4 pulled the PTRR process into the RAM’s built in refresh circuitry so it’s transparent to the memory controller.
RAM storage cells are tiny, fast, and don’t degrade over time. Each cell can store an electrical charge that distinguishes a 0 from a 1. However they forget their contents whenever they’re being read or if they’re not topped up occasionally. RAM needs to be refreshed by writing back contents after a cell is read, and making sure that periodically every cell in the chip is read and written back. Without constant power to refresh, RAM forgets its contents.
Flash is similar to RAM because it also stores data as a charge. To make the contents last without power and survive being read, each cell is tied to the gate of a MOSFET transistor. The MOSFET is like an amplifier in that it takes the small charge at the input and controls a larger signal without depleting the input charge. Think of the cell as a light switch: the switch stays in the same position no matter how much electricity passes through. The part that stores the charge and makes the flash MOSFET different from a normal MOSFET used in other electronics is called the floating gate. This is made of layers just a few atoms thick of insulators and conductors.
The catch is in programming and erasing the cell. To make the flash cells last, you need to eliminate any possible conductive path in or out of the charge storing part of the cell. Programming a flash cell to a 0 (flash is a “1” in it’s erased state, the N in NOR and NAND flash stands for “not”, i.e. negative logic) requires pushing a high voltage onto the MOSFET, causing it to conduct just enough to push some electrons into the MOSFET’s floating gate. Erasing requires an even higher voltage applied in a different way to drain the charge out. Both processes take advantage of normally undesirable features of MOSFETs called breakdown, where a high enough voltage causes it to conduct in ways it wouldn’t in normal operation.
Those high voltages, particularly the erase voltage, cause permanent wear on the floating gate and MOSFET, causing the charge to leak faster than normal. Even flash that’s not written or erased often isn’t perfect and a programmed cell will degrade over many years from a 0 to a 1. There is a whole science to counteracting flash wear and inevitable errors that I won’t go into here. The SSD controller chip is responsible for managing wear and data integrity, which is why you sometimes hear about SSDs that could lose your data if you don’t have a bugfixed firmware.
There are other technologies that are available that could replace flash. MRAM stores magnetically and is immune to wear from writing, not unlike core memory used in computers from the '50s through the '70s. FeRAM is similar to MRAM but less dense. You already have FeRAM in your car’s dash to store the constantly updating mileage, as it’s immune from damage by that constantly updating number or automotive temperature extremes. Phase change memory stores by heating tiny chunks of a crystalline material to get it to change it’s structure. Intel used this in its now-defunct 3D Xpoint memory. Memristor is another that takes advantage of a relatively new kind of electronic component type.
All of these new technologies are better than flash in longevity and many are close to RAM in performance. However none yet can be made as dense as RAM or as cheaply as flash. Memristor and MRAM are both frontrunners for replacing both RAM and flash, but it’s only fairly recently that fabs started offering the processing steps needed to make these in high density devices.
Wrote a TSR to beep the speaker gradually longer every time a key is pressed. The programming teacher assumed excessive beeping meant you were playing some sort of game. I’d run it on the PC I was using before class was over to get the next kid to sit there in trouble.
If you’re piping any of those commands to or from awk, you can also go.