4 ms·

(Intensity) = (Power) / (Unit Area) (Sun's Radius) = 695 x 10^6 m (Sun's Power) = 4 x 10^26 W (CPU Output) = 75 W (Die Size) = 37 mm x 37 mm (Sun Intensity

(Intensity) = (Power) / (Unit Area) (Sun's Radius) = 695 x 10^6 m (Sun's Power) = 4 x 10^26 W (CPU Output) = 75 W (Die Size) = 37 mm x 37 mm (Sun Intensity) = (4 x 10^26 W ) / (4 x pi x (695 x 10^6 m)^2) ~ 66 x 10^6 (CPU Intensity) = (75 W) / (0.0014 m^2) ~ 53 x 10^3 I'm getting a several orders of magnitude higher W/m output for the sun. Perhaps I made an algebra mistake?

namibj 8y ago
Yes. You can handle 100W on a 300mm^2 chip. Or 300W on a large one, compare AMD Ryzen/ Nvidia Volta (MXM/V100).
- nine_k 8y ago
  this gives 3.46e+5, probably comparable to brown dwarf figures in the tread.
  - namibj 8y ago
    Sounds higher than a nuclear reactor, for which you can find data on nucleate boiling without forced flow to support about 10W/cm^2 without much risk of reaching critical heat flux (in the strict sense, as you then transition to a vapor isolation due to the surface rapidly heating beyond the temperature where nucleate boiling is sustained, and from what I remember/believe, you won't transition back without reducing the surface temperature to be below that at critical heat flux, possibly even lower due to the lack of agitation/uniformity of the vapor layer). I did some research into what can be archived with suitable dielectric fluids and nucleate boiling to allow much higher heat flux on the surface of the silicon without requiring any energy input to actually separate hot and cold, but allowing the use of pumps and such to provide forced flow on the silicon. It seems that if you have a nozzle to provide sufficient flow speeds across the die you can get higher critical heat flux than can be reasonably handled through the power pins on an AMD EPYC socket, which has some limitations due to the LGA technology used for the contacts. A zero-insertion-force PGA socket should not be bound by this limit of temperature rise at the contact of the LGA spring/pin and the chip contact pad due to resistive heating resulting in the contact pressure declining (due to the spring weakening), which yields a feedback loop that can jump over to a domino effect on the other nearby power pins. I remember the flow rate being proportional to the critical heat flux as well as the distance the flow from the nozzle has to cross and provide cooling for. There were speeds of iirc. about 20m/s if one were to cool a delidded AMD EPYC at maximum power draw @4GHz, or rather, extrapolating from what can be archived with a die surface temperature of 50 degree Celsius. So, yeah, the heat flux is actually a problem, but I think one could integrate some sensors and sufficiently fast switches that shut the section of the die off if the temperature reaches dangerous levels (and do so fast enough to not damage anything, i.e. microseconds or what time there is), and use such a test chip to engineer a forced-flow direct-die (or maybe even with a heat spreader on top, but that costs you due to the nucleate boiling not going below 20 kelvin temperature loss, and additional system losses in the radiator/heat exchanger as well as pipes likely resulting in costs of about 5 additional kelvin). This could open the door to operating CPU dies at much, much higher power densities than currently normal. It's like a heat pipe on steroids. One would want circuity in the CPU to rapidly shut down in case the temperature rises quickly, as regardless of why this happens, not doing so will literally blow a hole in the chip before you can drain the inductors providing smooth power to the socket.
Tuna-Fish 8y ago
Your CPU is huge. For example, the highest-performance single-chip Pinnacle ridge (AMD Ryzen 2 2700X) is 213 mm² and has a TDP of 105W. That's roughly an order of magnitude difference.

namibj 8y ago

Yes. You can handle 100W on a 300mm^2 chip. Or 300W on a large one, compare AMD Ryzen/ Nvidia Volta (MXM/V100).

nine_k 8y ago
this gives 3.46e+5, probably comparable to brown dwarf figures in the tread.
- namibj 8y ago
  Sounds higher than a nuclear reactor, for which you can find data on nucleate boiling without forced flow to support about 10W/cm^2 without much risk of reaching critical heat flux (in the strict sense, as you then transition to a vapor isolation due to the surface rapidly heating beyond the temperature where nucleate boiling is sustained, and from what I remember/believe, you won't transition back without reducing the surface temperature to be below that at critical heat flux, possibly even lower due to the lack of agitation/uniformity of the vapor layer). I did some research into what can be archived with suitable dielectric fluids and nucleate boiling to allow much higher heat flux on the surface of the silicon without requiring any energy input to actually separate hot and cold, but allowing the use of pumps and such to provide forced flow on the silicon. It seems that if you have a nozzle to provide sufficient flow speeds across the die you can get higher critical heat flux than can be reasonably handled through the power pins on an AMD EPYC socket, which has some limitations due to the LGA technology used for the contacts. A zero-insertion-force PGA socket should not be bound by this limit of temperature rise at the contact of the LGA spring/pin and the chip contact pad due to resistive heating resulting in the contact pressure declining (due to the spring weakening), which yields a feedback loop that can jump over to a domino effect on the other nearby power pins. I remember the flow rate being proportional to the critical heat flux as well as the distance the flow from the nozzle has to cross and provide cooling for. There were speeds of iirc. about 20m/s if one were to cool a delidded AMD EPYC at maximum power draw @4GHz, or rather, extrapolating from what can be archived with a die surface temperature of 50 degree Celsius. So, yeah, the heat flux is actually a problem, but I think one could integrate some sensors and sufficiently fast switches that shut the section of the die off if the temperature reaches dangerous levels (and do so fast enough to not damage anything, i.e. microseconds or what time there is), and use such a test chip to engineer a forced-flow direct-die (or maybe even with a heat spreader on top, but that costs you due to the nucleate boiling not going below 20 kelvin temperature loss, and additional system losses in the radiator/heat exchanger as well as pipes likely resulting in costs of about 5 additional kelvin). This could open the door to operating CPU dies at much, much higher power densities than currently normal. It's like a heat pipe on steroids. One would want circuity in the CPU to rapidly shut down in case the temperature rises quickly, as regardless of why this happens, not doing so will literally blow a hole in the chip before you can drain the inductors providing smooth power to the socket.

Tuna-Fish 8y ago

Your CPU is huge. For example, the highest-performance single-chip Pinnacle ridge (AMD Ryzen 2 2700X) is 213 mm² and has a TDP of 105W. That's roughly an order of magnitude difference.