Coolant flow control

1 . A circuit system, comprising:

a plurality of circuit board systems, wherein each circuit board system of the plurality of circuit board systems comprises:

a circuit board,

a plurality of integrated circuit (IC) chips mounted on the circuit board,

a cold plate thermally coupled to the circuit board,

a first conduit extending through the cold plate, the first conduit configured to convey a flow of a coolant, wherein the first conduit is arranged such that the flow of the coolant through the first conduit is configured to heat and cool the circuit board,

a valve configured to control a rate of the flow of the coolant through the first conduit,

a controller configured to:

receive a first temperature from at least one of the plurality of IC chips,

based on the first temperature, control the valve to decrease the rate of the flow of the coolant to allow the plurality of IC chips to heat to a target operating temperature range,

after controlling the valve to decrease the rate of the flow of the coolant, receive a second temperature from the at least one of the plurality of IC chips, wherein the second temperature is greater than the first temperature, and

based on the second temperature, control the valve to increase the rate of the flow of the coolant to cool the plurality of IC chips and maintain the plurality of IC chips at the target operating temperature range, and

an enclosure housing the circuit board, the cold plate, and the controller; and

a coolant source configured to supply the coolant to the plurality of circuit board systems in parallel.

2 . The circuit system of claim 1 , wherein the controllers of the plurality of circuit board systems are configured to control the valves of the plurality of circuit board systems independently from one another.

3 . The circuit system of claim 1 , comprising a heat exchanger configured to receive the coolant from each of the plurality of circuit board systems in parallel.

4 . The circuit system of claim 1 , wherein the coolant source comprises one or more pumps configured to push the coolant through the circuit system.

5 . The circuit system of claim 1 , wherein each circuit board system of the plurality of circuit board systems comprises:

a second conduit configured to convey a second flow of the coolant from a common inlet with the first conduit of the circuit board system, wherein the second flow bypasses the first conduit of the circuit board system,

wherein the controller of the circuit board system is configured to control the valve to adjust the rate of the flow and a second rate of the second flow by adjusting the flow through the first conduit and the second flow through the second conduit.

6 . The circuit system of claim 5 , wherein, for each circuit board system of the plurality of circuit board systems, the valve is positioned in the second conduit.

7 . The circuit system of claim 5 , wherein, for each circuit board system of the plurality of circuit board systems, the valve is positioned in the first conduit.

8 . The circuit system of claim 5 , wherein, for each circuit board system of the plurality of circuit board systems,

the second conduit bypasses the cold plate.

9 . The circuit system of claim 5 , wherein each circuit board system of the plurality of circuit board systems comprises a flow restrictor configured to restrict the second flow of the coolant through the second conduit.

10 . The circuit system of claim 9 , wherein, for each circuit board system of the plurality of circuit board systems, the flow restrictor is positioned in the second conduit.

11 . The circuit system of claim 10 , wherein, for each circuit board system of the plurality of circuit board systems, the flow restrictor comprises a member that fills a cross-section of the second conduit and comprises one or more holes having a smaller total cross-sectional area than a cross-sectional area of the second conduit.

12 . The circuit system of claim 1 , wherein, for each circuit board system of the plurality of circuit board systems, the valve comprises a binary valve.

13 . The circuit system of claim 1 , wherein each circuit board system of the plurality of circuit board systems comprises:

a power supply unit configured to provide power to the plurality of IC chips; and

a third conduit configured to convey a third flow of the coolant to cool the power supply unit, wherein the flow of the coolant through the first conduit is from the third conduit.

14 . The circuit system of claim 13 , wherein, for each circuit board system of the plurality of circuit board systems, a second flow rate of the coolant through the third conduit is substantially insensitive to adjustment by the valve.

15 . The circuit system of claim 13 , wherein each circuit board system of the plurality of circuit board systems comprises:

a second cold plate that is thermally coupled to the power supply unit,

wherein the third conduit extends through the second cold plate.

16 . The circuit system of claim 1 , wherein, for each circuit board system of the plurality of circuit board systems, the controller is configured to:

determine a future computation frequency or future power supply voltage of at least one of the plurality of IC chips;

predict at least one temperature of the plurality of IC chips based on the predicted future computation frequency or future power supply voltage; and

control the valve based at least on the predicted at least one temperature.

17 . The circuit system of claim 1 , wherein each circuit board system of the plurality of circuit board systems is configured such that a total flow rate of the coolant through the circuit board system varies by 20% or less over a full range of settings of the valve.

18 . The circuit system of claim 1 , wherein, for each circuit board system of the plurality of circuit board systems, the plurality of IC chips are configured to perform a common type of computation in parallel with one another,

wherein the common type of computation comprises a hash computation or a machine learning computation.