1. T-simulation
OUTLINE
Inputs to the T-simulation: chips, boards, crate mechanics and fan
T-simulation performed into two steps:
On large scale: simple AM chip model, but full crate sim, AMB_V2 - Results
On small, deteailed scale: AM06 package detailed model inserted, AMB_V3, but simplified crate simulation- Results
Future cooling tests plan and conclusions

2. Detailed T-simulation (IMEC) for the new AMBSLP
 to know T on silicon!
Optimize chip package and boards dissipation
Estimate the temperature in the chip silicon knowing T just outside the package
ALL details must be taken into account
from package design
to crate, PS, fan design
Heat Sink
Die size
Die underfill
Substrate
RDL
Tall DC-DC converters
in the middle
AMB with four LAMBs model
LAMB
model
Crate &
fan model
What we have understood is that in the crate the pcb is hot and the air is very cold. This happens because the resistors do not exchange heat with the air.
So these boards full of resistors are good to stress the power but not so good to emulate the behavior of the final Associative Memory Boards.
Now we are repeating the test with 3 AMBboards full of old Amchips, with mechanical and termal characteristics more similar to the final ones.
We will use also a different fans module, the Wiener Hyper Blower, to avoid the hot spots and maximixe the air flux.
Understanding the importance of the package and PCB design to optimize the heat dissipation, we asked also to IMEC a temperature simulations at the chip, board and global system level.

3. NOVEMBER 2014 SIMULATION Inputs - AMB_V2 Large Artix FPGAs DC-DC 1,2 V

4. Air flow in the crate simulation
Not efficiently cooled slots
Bad
slots

5. Next to
Worse AM pos
Worse AM pos

6. 10 m/s Simulated As uniform 4 m/s Simulate the Worse case (blue) with
Max=3,2 & 4 m/s

7. AMB_V2
Full crate sim
Simple AM06
Lower air flux

8. 94.5o
Inside the red box: max T = 94.5o
Inside the black box: max T = 79o max in the
Bad slots with red arrows (on the left of the box)
On the right part of the black box (good slots)
T= 61o, 67o, 72o, 73o, 70o, 69o, 75o and 64o
These are temperatures in good slots where the DC-DC is far.

9. NEW T-SIMULATION March 2015 Improving the AMBSLP layout
Detailed model for AM package (see next slides)
AMB_V2
AMB_V3
New inputs to the simulation
TOT= 247W

12. AM chip + PCB piece
With air flow (4 m/s)
Results
39,75
Results

13. 55 C

14. 99,4
Worse slot
99 degree on
Die is acceptable

15. 88
Near to worse-slot
88 degree on
Die is acceptable

16. 3 slots are even worse than worse simulated case
CPU position + 2 SSB
Worse case shown
Other 3 slots have similar behaviour as worse cases shown by T-sim
2 SSB + 1AM
Max T ~99 ±5 degrees, acceptable
However it is a conservative estimate:
Average flux larger than the simulated one
The simulation does not allow the x component of air velocity
Lowering the fan with respect the crate  more uniform flux

17. Conclusions
The AM06 package has very low resistance: die T ~ package-PCB T.
Conservative simulation predicts TMax AM06 die ~99o  ok
Lowering the fan or using a diffusor we can have a more uniform flux of air, uniform temperature, and lower TMax
We will do new cooling tests to see if the T differences between slots detected by the T-sim correspond to the observed differences
We will measure the temperatures for different setups of the free space available in the rack.