4 ms·

If I understand this correctly, he uses a SIMD instruction since that switches the most number of transistors at the same time and causes a tiny ripple in chip

If I understand this correctly, he uses a SIMD instruction since that switches the most number of transistors at the same time and causes a tiny ripple in chip power line. The receiver sees an aliased version of one of the harmonics. But why is the radiation not shielded by the computer? We have tons of regulation for this kind of stuff AND a metal body that should stop most of the signal.

colechristensen 6y ago
Everything is an antenna, no shielding is perfect. Engineering circuits to reduce EM is actually very difficult, and gets more difficult as you desire less radiation. The regulations are generally about “harmful” interference and being detectable over a short distance isn’t that.
jrockway 6y ago
Radio receivers are very sensitive and you're very close to your computer, both factors that make shielding difficult. And, the shielding isn't perfect -- there are holes for fans, some cases are made out of glass instead of metal, etc. There are regulations, but they don't mandate perfect attenuation. They only specify that your emissions shouldn't interfere with licensed users. Since the licensed users are pretty far away from your computer and the power is very low, it's generally not a problem. (As for sensitivity, remember that GPS signals have a power of something like 10^-16 watts at the surface of the earth, and you can receive those just fine. Radios are very sensitive instruments!)
LinuxBender 6y ago
FWIW, modern PC cases are mostly plastic and clear plexiglass to show off all the RGB LED's.
andi999 6y ago
Just a EU perspective here. There are EMC directives and norms, they generally work like this: the amount allowed for emission needs to be accepted without disturbance (there are two different categories like industrial and non-industrial). Let me give you an example. non-industrial is not allowed to emmit more than 3V/m, but non industrial product are also not allowed to be disturbed by 3V/m. So far so good. This only applies to 'disturbances' or 'non use signals'. Let me explain: Now, radio transmission is different (like a mobile phone). The use signal (which is not a disturbance) is allowed to be much higher, like 40V/m. (So there was a case where a coffee machine broke when putting the mobile on it). This is all in perfect compliance. (of course the manufacturer of the coffee machine hardened the device, but this was market forces). So for the other direction, I am not too sure but it can perfectly fine that the allowed EMC disturbs the reception of a radio signal device. Also EMC is only tested in 'typical' situations. About the legality by using Software to intentionally transmit signal (def not legal without HAM license or proper FCC testates) I have no idea who would be the liable party i n this case.
buckminster 6y ago
This is much better than it used to be. Back in the 80s we had an 8-bit computer and a 50s vacuum cleaner. Using the cleaner anywhere in the house would corrupt the computer's memory.

colechristensen 6y ago

Everything is an antenna, no shielding is perfect. Engineering circuits to reduce EM is actually very difficult, and gets more difficult as you desire less radiation. The regulations are generally about “harmful” interference and being detectable over a short distance isn’t that.

jrockway 6y ago

Radio receivers are very sensitive and you're very close to your computer, both factors that make shielding difficult. And, the shielding isn't perfect -- there are holes for fans, some cases are made out of glass instead of metal, etc. There are regulations, but they don't mandate perfect attenuation. They only specify that your emissions shouldn't interfere with licensed users. Since the licensed users are pretty far away from your computer and the power is very low, it's generally not a problem. (As for sensitivity, remember that GPS signals have a power of something like 10^-16 watts at the surface of the earth, and you can receive those just fine. Radios are very sensitive instruments!)

LinuxBender 6y ago

FWIW, modern PC cases are mostly plastic and clear plexiglass to show off all the RGB LED's.

andi999 6y ago

Just a EU perspective here. There are EMC directives and norms, they generally work like this: the amount allowed for emission needs to be accepted without disturbance (there are two different categories like industrial and non-industrial). Let me give you an example. non-industrial is not allowed to emmit more than 3V/m, but non industrial product are also not allowed to be disturbed by 3V/m. So far so good. This only applies to 'disturbances' or 'non use signals'. Let me explain: Now, radio transmission is different (like a mobile phone). The use signal (which is not a disturbance) is allowed to be much higher, like 40V/m. (So there was a case where a coffee machine broke when putting the mobile on it). This is all in perfect compliance. (of course the manufacturer of the coffee machine hardened the device, but this was market forces). So for the other direction, I am not too sure but it can perfectly fine that the allowed EMC disturbs the reception of a radio signal device. Also EMC is only tested in 'typical' situations. About the legality by using Software to intentionally transmit signal (def not legal without HAM license or proper FCC testates) I have no idea who would be the liable party i n this case.

buckminster 6y ago

This is much better than it used to be. Back in the 80s we had an 8-bit computer and a 50s vacuum cleaner. Using the cleaner anywhere in the house would corrupt the computer's memory.