alt.hn

2/20/2026 at 5:06:40 AM

Reading the undocumented MEMS accelerometer on Apple Silicon MacBooks via iokit

 https://github.com/olvvier/apple-silicon-accelerometer

by todsacerdoti

2/20/2026 at 7:38:01 AM

Way back in ~2008 I wrote the Newton Virus https://www.everita.com/how-the-newton-virus-was-made + https://www.youtube.com/watch?v=eh75j6OHhRc (sorry for the broken images, need to update that site). Between that and using a hidden API to take screenshots of each individual element on your desktop (from icons, to taskbar, to windows) the effect was pretty believable. One of the most fun (and frustrating) projects I ever worked on.

by seductivebarry

2/20/2026 at 1:22:51 PM

I've tried to find this for so long. I remember seeing it at the time as a teenager and thinking it was SO COOL. Basically made me discover Apple and want a Mac. :)

by outadoc

2/20/2026 at 1:38:42 PM

When I saw the post the Newton Virus was the first thing I thought of. Thanks for making it. I remember showing my family the video and remarking about how cool it was.

by directmusic

2/20/2026 at 8:47:28 AM

Offtopic, but I have nostalgic feelings for the era of MacBook in the video

by swiftcoder

2/20/2026 at 8:26:38 AM

Troika! Hello from a friend in London :)

by tmslnz

2/20/2026 at 7:20:27 AM

>have a hard to find mems accelerometer managed by the sensor processing unit

How did OP even know that an accelerometer exists in the first place?

by krackers

2/20/2026 at 7:31:00 AM

The presence of the sensor is well documented as part of Apples Sudden Motion Sensor hard drive protection system.

How to access it is undocumented.

by rustyhancock

2/20/2026 at 7:43:28 AM

Aaackshually, the Sudden Motion Sensor was introduced on 2005 in the PowerBook G4, and continued through the intel MacBooks with hard drives.

While officially undocumented, people figured out how to access it back then, with novel uses like smacking your MacBook to change spaces (virtual desktops) or swinging the Mac around to make lightsaber noises.

- https://www.youtube.com/watch?v=6uvQTTPr9Rw

- https://osxdaily.com/2006/12/06/macsaber-turn-your-mac-into-...

(I should know, I was in university back then and swung my Mac around like an idiot, lol.)

On the first Retina MacBook Pro 15" in 2012, and moving forward with all MacBooks that were SSD-only, they removed the SMS as it was not needed.

To my knowledge, this is the first time we're hearing that Apple Silicon machines have an accelerometer on the SoC, officially or otherwise. It's also certainly not branded or marketed as the SMS was. (https://support.apple.com/en-us/100871)

Happy to be corrected on this!

by future10se

2/20/2026 at 1:31:28 PM

In 2022 "a little birdy pointed out an accelerometer" to iFixit on their teardown of an M2 MBA: https://www.ifixit.com/News/62674/m2-macbook-air-teardown-ap...

They could not figure out what it was for.

Ars Technica commenters at the time believed it was to record drops so Apple repair teams could rebuff requests :)

by lelandfe

2/20/2026 at 10:21:30 AM

I think there's some sort of motion sickness reducing feature in MacOS Tahoe which would require an accelerometer.

by 1e1a

2/20/2026 at 7:52:02 AM

Given that current drives don't have moving parts, what function is this serving today?

by nerdsniper

2/20/2026 at 10:54:49 AM

Void warranty if dropped

by juggerl6

2/20/2026 at 1:06:32 PM

Has anyone reported this happening?

by nerdsniper

2/20/2026 at 6:22:00 PM

People who knew what they did aren’t going to go online and say that they tried to return a dropped device.

by xattt

2/20/2026 at 8:50:50 AM

Apple has a motion sickness mitigation feature that displays dots on your screen that move based on physical motion, so it’s fairly well known that the accelerometer exists.

by argsnd

2/20/2026 at 11:17:03 AM

That's for iOS devices though

by mschuster91

2/20/2026 at 2:32:53 PM

https://support.apple.com/en-om/guide/mac-help/mchla3c4f1da/...:

“Vehicle Motion Cues

Vehicle Motion Cues may help reduce vehicle motion sickness while using a Mac and riding as a passenger in a car or other on-road vehicle.

To customize Vehicle Motion cues, click Customize Appearance, then set any of the following options:

- Pattern: Select Regular for a stable and predictable pattern of onscreen dots, or Dynamic for a more engaging visual experience.

- Color: Select a color of onscreen dots. Color saturation will automatically adjust to maintain contrast with the content behind each dot.

- Larger dots: Turn on Large dots to increase the size of the dots that appear onscreen.

- More dots: Turn on More dots to increase the number of dots that appear onscreen.

Note: This option is available on Mac laptop computers. It’s not available on MacBook Air (M1) or 13-inch MacBook Pro (M1) or earlier.”

by Someone

2/20/2026 at 12:09:21 PM

It’s also for macOS

by angulardragon03

2/20/2026 at 12:15:59 PM

No.

by nom

2/20/2026 at 7:59:02 AM

> the sensor lives under AppleSPUHIDDevice in the iokit registry, on vendor usage page 0xFF00, usage 3. the driver is AppleSPUHIDDriver which is part of the sensor processing unit.

by saagarjha

2/20/2026 at 7:14:37 AM

undocumented

The one thought that comes to mind is this: "Your warranty claim was denied because we determined that the laptop was subjected to a sudden shock."

by userbinator

2/20/2026 at 7:23:04 AM

Back in the days this was to lock up the hard disk read/write head. Maybe a relic from those times instead?

by consp

2/20/2026 at 7:34:20 AM

Apple is not known for backwards-compatibility, and they were already using SSDs in their laptops long before switching to ARM.

by userbinator

2/20/2026 at 7:19:34 AM

idk you can just use simple liquid-container or sticker?

maybe apple was preparing for "carrying-around laptop experience"?

by sysguest

2/20/2026 at 7:25:16 AM

That's an entirely different product build path compared to the electronics production line though.

If a pick and place machine can drop it on and reflow it, that's what you want.

by XorNot

2/20/2026 at 7:45:19 AM

well it would be hardened when contact with air or something

see "Shipping Damage Indicators"

by sysguest

2/20/2026 at 7:20:08 AM

Did it park the drive heads?

by altairprime

2/20/2026 at 10:50:07 AM

On my M4 14-inch MacBook Pro, it looks like there are two accelerometers: One with {"DeviceUsagePage"=0xff00,"DeviceUsage"=3}, and one with {"DeviceUsagePage"=0xff00,"DeviceUsage"=9} - They both identify as Bosch BMI286

by 1e1a

2/20/2026 at 11:48:47 AM

Ah, after some testing, it looks like these both refer to the same IMU, DeviceUsage=3 is for the accelerometer and DeviceUsage=9 is for the gyroscope. The serial number is also the same for both.

by 1e1a

2/20/2026 at 8:27:41 AM

If it can read your heartbeat from your wrists resting next to the trackpad, maybe it can use that as a user satisfaction signal for gratuitous UI changes.

by JSR_FDED

2/20/2026 at 8:45:32 AM

If it's sensitive enough to read a heart beat, then surely it can be used as a covert microphone?

by pbhjpbhj

2/20/2026 at 11:43:12 AM

The laptop also contains a normal microphone. You can't access this without root; if you have that you have permissions to access the real microphone.

by gavinsyancey

2/20/2026 at 12:19:06 PM

... but think how much "engagement" a "security expert" would get out of this!

by nottorp

2/20/2026 at 11:02:16 AM

From testing, it seems to require me to press my wrists quite hard against the macbook to get a somewhat accurate reading on the heartbeat. Non the less a cool project and I wasn't even aware my macbook has an accelerometer.

by Quppi

2/20/2026 at 9:13:48 AM

Depends on the bandwidth.

by rcxdude

2/20/2026 at 9:13:40 AM

depends on the bandwidth

by rcxdude

2/20/2026 at 12:49:13 PM

I would like an app to lock my screen on sudden movement; optionally disable TouchID for next login.

by 47282847

2/20/2026 at 12:52:20 PM

Maybe you’re also interested in having it start the fuse on your thermite pot, that you have time to stop if it turns out it’s not the FBI raiding your house for what’s on your hard drive?

by ohyoutravel

2/20/2026 at 1:17:09 PM

Are you implying that it is paranoid and irrational regardless of circumstance to want this?

Sorry to disappoint. I’m working in the human rights space, with dozens of real world experiences by people I work with. I got raided once myself. They were unable to locate any computer on my premises. They however took my phone and a couple of encrypted hard drives for forensic analysis. They asked for the device PIN, which I did not provide. A court later ruled the raid and seizure and temporary confinement illegal. I did not reuse the returned phone. They didn’t pay for the replacement, or the lawyer.

by 47282847

2/20/2026 at 4:56:12 PM

Yes that was my implication, but I see based on your comment you have real concerns! My apologies for the implication.

by ohyoutravel

2/20/2026 at 10:02:25 PM

this is the best internet argument

by hansum

2/20/2026 at 10:29:03 AM

I've been wondering about this for a while, glad someone's finally managed to access it.

by 1e1a

2/20/2026 at 8:14:48 AM

Could this be used as "shake your mac for highly random seed" bits?

by ggm

2/20/2026 at 3:26:57 PM

There's lots of noise in the accelerometer readings, even without shaking

by 1e1a

2/20/2026 at 12:04:33 PM

Shake your Mac to undo would be consistent with iPhone, iPad, Vision Pro. Yes, you shake your head to undo when wearing AVP.

by mlajtos

2/20/2026 at 12:08:27 PM

This is a milder version of “Shake to Reboot” which is standard for all Etch-a-Sketch models

by RupertSalt

2/20/2026 at 9:11:43 AM

Probably not as random as you want it to be.

by c22

2/20/2026 at 9:14:09 AM

well wouldn't it add up?

someWhatRandom1 xor someWhatRandom2 xor notRandom3 xor ...

should be more 'random' than just 'someWhatRandom1'

by sysguest

2/20/2026 at 9:49:55 AM

i'm not sure it would necessarily be more random if you're mixing in a lower-entropy source which the accelerometer probably is

by throawayonthe

2/20/2026 at 9:54:12 AM

XOR is the worst hashing function imaginable, especially if the data isn't truly random, because it can cancel out to become even less random!

It's better to use a KDF or something. Even a block cipher should work far better than XOR.

by LoganDark

2/20/2026 at 1:31:44 PM

This is so cool thank you!

by thenthenthen

2/20/2026 at 9:53:12 AM

I wonder if this sensor is used for Vision Pro display mirroring.

by LoganDark

2/20/2026 at 10:22:33 AM

I think it's used for the motion sickness reducing feature in MacOS Tahoe that puts a bunch of dots on your screen that react to motion.

by 1e1a

2/20/2026 at 6:40:53 AM

[dead]

by baybal2