我全新安装了 ubuntu 12.04.4 LTS 和 CUDA 5.5 以及 nvidia-331.20 驱动程序。板上有 4 个 GeForce GTX 780。 X运行在集成卡上，而Nvidia卡则叠加起来做一些计算。
我注意到，无论温度如何，当不对其执行计算时，第三个卡风扇旋转为 0：
当一些计算时：
+------------------------------------------------------+
| NVIDIA-SMI 331.20 Driver Version: 331.20 |
|-------------------------------+----------------------+----------------------+
| GPU Name Persistence-M| Bus-Id Disp.A | Volatile Uncorr. ECC |
| Fan Temp Perf Pwr:Usage/Cap| Memory-Usage | GPU-Util Compute M. |
|===============================+======================+======================|
| 0 GeForce GTX 780 Off | 0000:02:00.0 N/A | N/A |
| 46% 80C N/A N/A / N/A | 93MiB / 3071MiB | N/A Default |
+-------------------------------+----------------------+----------------------+
| 1 GeForce GTX 780 Off | 0000:03:00.0 N/A | N/A |
| 47% 80C N/A N/A / N/A | 93MiB / 3071MiB | N/A Default |
+-------------------------------+----------------------+----------------------+
| 2 GeForce GTX 780 Off | 0000:83:00.0 N/A | N/A |
| 43% 79C N/A N/A / N/A | 93MiB / 3071MiB | N/A Default |
+-------------------------------+----------------------+----------------------+
| 3 GeForce GTX 780 Off | 0000:84:00.0 N/A | N/A |
| 48% 80C N/A N/A / N/A | 93MiB / 3071MiB | N/A Default |
+-------------------------------+----------------------+----------------------+
计算结束后立即：
+------------------------------------------------------+
| NVIDIA-SMI 331.20 Driver Version: 331.20 |
|-------------------------------+----------------------+----------------------+
| GPU Name Persistence-M| Bus-Id Disp.A | Volatile Uncorr. ECC |
| Fan Temp Perf Pwr:Usage/Cap| Memory-Usage | GPU-Util Compute M. |
|===============================+======================+======================|
| 0 GeForce GTX 780 Off | 0000:02:00.0 N/A | N/A |
| 38% 73C N/A N/A / N/A | 10MiB / 3071MiB | N/A Default |
+-------------------------------+----------------------+----------------------+
| 1 GeForce GTX 780 Off | 0000:03:00.0 N/A | N/A |
| 38% 73C N/A N/A / N/A | 10MiB / 3071MiB | N/A Default |
+-------------------------------+----------------------+----------------------+
| 2 GeForce GTX 780 Off | 0000:83:00.0 N/A | N/A |
| 38% 73C N/A N/A / N/A | 10MiB / 3071MiB | N/A Default |
+-------------------------------+----------------------+----------------------+
| 3 GeForce GTX 780 Off | 0000:84:00.0 N/A | N/A |
| 0% 75C N/A N/A / N/A | 10MiB / 3071MiB | N/A Default |
+-------------------------------+----------------------+----------------------+
是什么原因导致卡迷出现这种行为？