3 ms·
> A key performance metric of computers is their energy dissipation. One contribution to dissipation is friction at the rotary joints in each logic gate. Due
by darkmighty 9y ago
> A key performance metric of computers is their energy dissipation. One contribution to dissipation
is friction at the rotary joints in each logic gate. Due to the joint’s small frictional drag, mechanical
computers constructed from them can, in principle, dissipate orders of magnitude less power than
conventional semiconductor computers, while still operating at relatively high speeds.
This claim seems dubious, perhaps someone has more expertise to comment. The justification
> Operating this lock involves rotation at the joints by up to ∆θ≈1 rad. The model system analyzed in [11] is an excerpt of the links and joints shown in the closeup on the right of Figure 24. From [11, Eq. 2], this rotation dissipates bout 2.4×10−27J per rotary joint when operating at f = 100 MHz.
Seems akin to saying "We operate our microchip at 1 microvolt / 1 pico ampere at f=100MHz, giving 10-26J per operation." -- which seems like a silly aspiration without carefully analyzing noise and quantum mechanical constraints. (without which it would seem almost any computing device could operate at arbitrarily low power).
- pjc50 9y agoHowever it would have a nice property: not operating would consume zero power. Useful for low-leakage cases or energy harvesting.
- sigstoat 9y agoit is possible to design microprocessors which can just utterly stop. https://en.wikipedia.org/wiki/Static_core https://en.wikipedia.org/wiki/Static_core power consumption doesn't drop to exactly zero, but it can come into competition with the quiescent current of the power supply.
- deepnotderp 9y agoThat's possible for conventional CMOS as well, one example is power gating. Not exactly zero leakage, but pretty damn close.
- QAPereo 9y agoThe keyword there is, “in principle,” which is even less than “on paper.” Essentially if you had elements which asymptotically approached frictionless interactions, and you had an idealized power source... sure, less entropy than firing electrons through Si. Things ignored to make that work: Materials which are likely to ever exist. A degree of mechanical perfection on the order of one of NASA’s fused quartz spheres. An idealized means of transferring energy to the device. A perfect vacuum. Perfect shielding from external influence, especially vibration. The faster you crank this up, the more energy is in the form of Ke in the device, and like a flywheel, it may come to resemble a bomb.