Why does my PC crash only when my cat is nearby? | Hacker News Reader

Why does my PC crash only when my cat is nearby?

superuser.com

63 pointstecholic30 comments

Hahaha, okay, I genuinely like StackOverflow but the comments there read like a parody.

The guy is asking for hypotheses and some guy is responding with hypotheses but then there are like two other guys who are all like "we don't know, this could be anything", one of whom goes up to the answerer and tells him his hypothesis is just guesswork.

Classic. These guys won't help or stay out of the way. Just injecting themselves in the conversation to be annoying.

Maybe OP should try using JQuery.

Pfft. What a silly statement to make. Clearly it is the cat that should be using JQuery...

that is deprecated, should have gotten a bengal instead. anyhow this wouldn't happen with lynx.

Have you ever tried using the bengal fork of cat? I mean its cute and lovable but my god it's alerts for your attention are worse then Vista's UAC...

The typical bad SO answer would be "but why do you have a cat in the first place? Dogs are much better."

And then the question being immediately closed.

Besides static (which seems likely - perhaps there is an issue with the grounding), I can think of two other explanations:

1) the computer is near a heater. The heat both attracts the cat and overwhelms the cooling enough to cause a crash.

2) The pc makes some noise (e.g. Coil whine) when it is about to crash, and the cat can hear that noise.

I have definitely seen issues where an unterminated reset line was susceptible to causing reboots from static electricity charges from people, chairs, etc. several feet away. Not even discharges, just charged objects moving around.

Perhaps the line to the reset jumper on the motherboard is not connected or is not grounded correctly and is acting as an antenna.

Issues like this usually involve 2-3 underlying issues. For example, #1, the cat, #2 faulty motherboard design without protection on the reset line, #3 bad wiring. Or something like that.

I'd get rid of the computer, or get rid of the cat. Depending on which one is a bigger problem.

The second is very possible. Maybe a defective PSU and the cat hears the components struggling and gets curious, hence the correlation.

I've had this one, but with a bunny. Carpet + Bunny + PC that stands on the floor, so each time bunny ran near the PC it caused a hard freeze due to statics.

I would guess that if this user spent enough weeks or months to learn the skills and tracked this down to a precise root cause, he/she would find out it is a floating input on some IC.

It might have a pull up/down resistor that has failed, or it might have too high a resistance, or it might have been missed off the design all together.

The fact it's a reboot rather than a freeze says there's a good chance some software or firmware is aware of the reason for the reboot too. OS level errors typically leave records (eg. BSOD's). Firmware reboots often have some kind of debug mode that you can change to a system halt and inspect stuff over some debug port with the right equipment.

My cat grew up sitting on my lap while I worked. He has learned, over the years, that when he wants me to stop and all else has failed, he merely has to jump on the keyboard. All kinds of things have happened from that action. Keeping good backups, scripts, and being able to restore from them in under an hour is important with a cat around.

This problem sounds more familiar to me. Cat - keyboard interaction is one of the most destructive, besides cat - carpet and cat curtain interactions..

Your cat is an ally making you adopt best practices by giving you a trial by fire. Your cat is red team.

Cat probably has a bad case of fleas. Local bug density goes through the roof -> System crashes.

Give the cat a flea bath, run your debugger, and say 7 Halt, don't Catch Fire's.

You owe the oracle a tube of Advantage.

Old story on the internet with cats turning off computers/laptops rubbing them, people generally blame static -

(1964) A Post Office expert called to investigate TV interference in Derby found the trouble came from a house where an elderly woman was building up static electricity — by stroking her cat. https://trove.nla.gov.au/newspaper/article/107507113

But if the cat really isn't touching it then I'm dubious. I can't see how static electricity could turn off a computer from a foot away.

Seems like ESD. The ESD event makes electrostatic fields, means you don't need to discharge directly into the circuits, a discharge onto the case of the PC will create very strong fields also inside of it. These short term fields can cause components to get a bit out of whack.

Wouldn't the case act something like a faraday cage, dissipating the fields enough not to cause an issue?

If the case isn't electrically grounded/earthed properly, the cat can create a strong enough electric charge in the case and conduct it to other components inside, causing a reboot.

In theory there is no difference between practice and theory, in practice, there is. While your computer case is designed to act as a Faraday cage (for EMI compliance reasons), this is only given when its new +some years old. Many opening/closings of the doors, disassembly/reassembly will wear out the conductive seals and eventually it wont perform as it was originally designed. Also, if the guy cut a big hole in the side to put a window in or something, that ruins the whole Faraday cage concept. Same goes if you put in a fan without a conductive filter closing the opening. ESD is in the GHz range and if you have any slots/holes in the case which are larger than the wavelength of the ESD, the fields will get inside.

I have caused two different computers to reboot on two different occasions due to touching the chassis and causing a (somewhat painful) static discharge. There were no other issues with the computers before or after. It's not surprising that they don't like momentary voltage surges going through their ground.

Could the cat wear one of those magnetic collars that allow access through a cat flap, and that magnet be the issue?

Is a very good hypothesis... hum

But, wouldn't be those magnets too small for create a strong current? The computer should be protected from common sources of interference, right?

Magnets need to be very strong or changing very quickly to affect electronics. They were a big concern with floppy disks and messed with CRTs but beyond that no magnet you're likely to come across is going to cause any effect on a PC (there are even strong ones in a lot of laptops). Even hard drives (the one common remaining magnetic component in systems) are unlikely to be affected.

I got the same problem but with my chair. Whenever I stand up, the chance is about 50/50 that it instantly restarts... I swapped the chair and it doesnt happen anymore. Swap the cat, maybe that'll help.

I can switch off street lamps by walking near them, I'd like to try with that computer.

Cats like warmth, and computers do not like warmth.

It's possible that the cat shows up when temperature is higher, and higher temperatures are more likely to make a computer crash.

When I was a kid, my cat would sit on top of the CRT monitor, because it was warm.

That's what I thought as well. Possibly also correlated with the time of day. Temperature and other possible factors vary over the course of the day and cats tend to be active at certain hours of the day. As a stupid example: some update service is set to check for updates between 5pm and 6pm. A bug in the update check causes crashes. The cat expects dinner at 5pm.

What, no “useless use of cat” responses?

Reply on news.ycombinator.com