3 ms·

Operating Systems exist to safely multiplex available resources, and make them available to the user for running programs. In my opinion, the closest analogy i

Operating Systems exist to safely multiplex available resources, and make them available to the user for running programs. In my opinion, the closest analogy is that of electrical power. In that world we have circuits and protection systems that have been standardized. The user interface at the end is an outlet of some form on a wall in a room. The circuit it is part of is protected against overload, and WILL NOT deliver more than the rated breaker output for more than a few cycles. Any Operating system has to at minimum, provide such a way to run a program. Our current options, Linux (even SELinux), MacOS, Windows, etc. do not offer a way for the user to dynamically assign processing time and resources (such as files, network addresses, etc) to a program.

tengwar2 4y ago
> The circuit it is part of is protected against overload, and WILL NOT deliver more than the rated breaker output for more than a few cycles. Actually it will, and it is required to do so. There are different classes of fuse and circuit breaker. The time to break the circuit depends on the class and the percentage overload, but think in terms of seconds to minutes, not cycles. The rationale for this is: A) With modern PVC insulation, the limit on continuous current is the continuous temperature. If it is too high, the wire core will slowly migrate through the PVC. Anything up to 90℃ is ok (British standards - and yes, I did check that!). Higher temperatures are ok for short periods because there will not be time for migration, but obviously you don't want to run it hot enough to cause fire ok allow fast migration. B) Electrical motors can have high inrush current when they start, but only for short periods. It makes more sense to dimension the wiring for the steady state, and use a show blow fuse or circuit breaker to guard against stall conditions. Still, the analogy is a good one. A few years ago I built a garage and had to have a Part P inspection done on the wiring, which included showing calculations which take account of the thermal environment (in free air, on wall, in tube with/without other cables etc.) and cable type to determine the maximum permitted current for that circuit. There was no "consenting adult" exception (although our legislation expressly permits non-professionals to do the job subject to Part P inspection).
- mikewarot 4y ago
  I knew as I wrote it, someone was going to pick apart the details... I tried to hedge my bets. The new arc protection breakers look interesting to me.
yellowapple 4y ago
The analogy comparing operating systems to electrical grids reminds me a lot of Multics, which was designed around the idea that computing power would be a public utility like electricity or water, and people would have home terminals connected to giant public mainframes. Of course, history didn't quite work that way, what with the proliferation of microcomputers - though sometimes I feel like the modern trend of web applications has managed to sloppily reinvent that idea.

tengwar2 4y ago

> The circuit it is part of is protected against overload, and WILL NOT deliver more than the rated breaker output for more than a few cycles. Actually it will, and it is required to do so. There are different classes of fuse and circuit breaker. The time to break the circuit depends on the class and the percentage overload, but think in terms of seconds to minutes, not cycles. The rationale for this is: A) With modern PVC insulation, the limit on continuous current is the continuous temperature. If it is too high, the wire core will slowly migrate through the PVC. Anything up to 90℃ is ok (British standards - and yes, I did check that!). Higher temperatures are ok for short periods because there will not be time for migration, but obviously you don't want to run it hot enough to cause fire ok allow fast migration. B) Electrical motors can have high inrush current when they start, but only for short periods. It makes more sense to dimension the wiring for the steady state, and use a show blow fuse or circuit breaker to guard against stall conditions. Still, the analogy is a good one. A few years ago I built a garage and had to have a Part P inspection done on the wiring, which included showing calculations which take account of the thermal environment (in free air, on wall, in tube with/without other cables etc.) and cable type to determine the maximum permitted current for that circuit. There was no "consenting adult" exception (although our legislation expressly permits non-professionals to do the job subject to Part P inspection).

mikewarot 4y ago
I knew as I wrote it, someone was going to pick apart the details... I tried to hedge my bets. The new arc protection breakers look interesting to me.

yellowapple 4y ago

The analogy comparing operating systems to electrical grids reminds me a lot of Multics, which was designed around the idea that computing power would be a public utility like electricity or water, and people would have home terminals connected to giant public mainframes. Of course, history didn't quite work that way, what with the proliferation of microcomputers - though sometimes I feel like the modern trend of web applications has managed to sloppily reinvent that idea.