"Simulated CPU Die Testing"
9/4/01
page 2
Summary: Simulated CPU die testing may be the "purest" measure of heatsink performance.
I continually look to improve the heatsink testing we do. As another test, you will see results using a simulated CPU die (T-Bird size), pictured above.
The simulated die is made of copper and was made by a machine shop to simulate mounting a heatsink on a socket. The three tabs on each side correspond to the location of a socket's lugs - this allows the same amount of pressure as when mounted on a motherboard.
In front of the block are the heaters used to simulate CPU temps. These are Minco #HK5578. I used four of these to better spread the load to the block. Arctic Silver epoxy was used to glue the heaters to the block's base.
The block weighs about 1200 grams/2 ¼ pounds; there are thermocouples in the simulated die and base to check temps.
The heaters are powered by a Laboratory Power Supply capable of producing up to 180 watts - more than enough to stress a heatsink. In preliminary testing, I ran heatsinks up to about 130 watts.
In running this tester, all four heaters are wired together so that they are powered equally through the power supply. The block is encased in foam insulation to mitigate heat loss to the air.
Testing reveals that heatsinks will show higher C/Ws than those found using actual CPUs and motherboards. This is due to two factors:
- All the heat from the power supply is concentrated in the block; there is very little heat loss from secondary heatpaths, in contrast to actual conditions, secondary heatpaths, such as through the CPU base, are significant cooling factors;
- CPU heating by using a program such as Prime 95 may not fully power the CPU, whereas the simulator is fully powering the block.
The table below compares the two approaches:
Simulated Die vs Actual Motherboard Testing
| Heatsink |
Motherboard |
Die |
Ratio |
| Antec |
0.39 |
0.58 |
1.49 |
| Dynatron |
0.19 |
0.28 |
1.47 |
| Fortis A102 |
0.19 |
0.29 |
1.45 |
| Tornado |
0.30 |
0.40 |
1.33 |
| Volcano |
0.25 |
0.33 |
1.32 |
Simulated die testing is clearly higher. The variation in results between the two (the Ratio in the chart) is due to the factors mentioned above plus the interactions between the heatsink and motherboard, which vary from each heatsink. The relative rankings are similar, however.
Readers can use the simulated die results as the "worst case" performance for any heatsink; the real world tests are indicative of results users may expect under similar circumstances in "real world" use.
Email Joe
