Be Quiet !

Our three crunching PCs are noisy ones ! Too noisy GPU haulers ! So I decided to find a solution for a quiet Cruncher. I do not like water (and chemicals) in computers, water-cooling was not an option. So I kept an eye out for another air-cooling possibility.

First Step - Replacing GTX 460
Palit (Nvidia) GeForce GTX 750 Ti KalmX
Factory overclocked but unlocked for further experiments ...
PCIe x16 Slot delivers enough power (75 W) so no additional Power cable is required !

Architecture: Maxwell 1 / 2 Slots
Bus Support: PCI-E 3.0 x16
TDP (Thermal Design Power): 60 Watt
Max. Core Temperature: 95 Degree Celsius
CUDA Cores: 640
Resolution: 4096 x 2160
Core Clock: 1020 MHz (Boost 1085 MHz)
Memory: 2048 MB GDDR5
Memory Clock: 1350 MHz (5400 effective)
Memory Interface Width: 128 Bit
Memory Bandwith: 86.4 GB/sec
Floating-point Performance: 1306 GFLOPS

Ordered two pieces GTX 750 Ti KalmX and installed them into the oldest PC (ID: 4546148 / Gigabyte Z68XP-UD3P / i7 2600K / 2 x GTX 460 OEM - GF104)
Newest Nvidia Driver 353.62 / BOINC 7.4.42 x64) / Win7 Home Premium up to date.

Tinkering with overclocking of GTX 750 Ti (EVGA Precision 4.2.1): I found stable configuration for GPU Clock: 1320 MHz (1020 + 300 MHz) / Memory Clock: 3155 MHz (2700 + 455 MHz). For proper working of cooling I added a 20 cm silent fan - protected by a metallic strainer (dust filter did not work) - to the side-cover of the tower. Resulting GPU Temperature: 53 degree Celsius (environment temp about 24 degree Celsius). With environment temperature climbing to near 40 degree Celsius GPU temperature will not exceed 58 degree ! Running 2 Parks Cuda55 tasks on each graphics card works fine for me.

Conclusion
(1) Only a faint noise of the PC fans is still audible !
(2) Temperature of the GPUs drastically lowered !
(3) Power consumption remarkable lowered - good for your purse !
(4) Less cable clutter due to no more needed additional power consumption cable 

Second Step - Mounting passive part of cooling system "Alpenföhn Peter 2" to the GPX 460
Notice: This cooling system is not really a passive system, normally it needs additional fans !

Dismounting the Fan-Cooler from GTX 460 board (frame and four screws on the backside) shows very crumbly Thermal Compound on the surface of the graphics chip and the cooler plate (contacting/cooling was probably bad). On one of the two cards I discovered a completely burnt Power MOS Fet. Due to melted/charred underground a replacement was not possible, so lost one GPX 460 !

Applying a thin film of Arctic MX-4 Thermal Compound to the graphics chip surface of the intact card and mounting the the passive cooler part by using the enclosed screws. All in all a very easy procedure !

Then I replaced one of the GPX 750 Ti KalmX (GPU 2) by the modified GTX 640 and removed all slot covers at the rear to allow best air flow provided by the big fan in the side-cover of the tower. GPX 640 as GPU 1 has been connected to the monitor. After starting the system BOINC was not able to communicate with the GPX 640, working of GPX 750 Ti was ok. I remembered some discussions at E@H Forum about this and found the solution in WIKI of Rechenkraft.de (BOINC server was down at this time). I added a new file cc_config.xml to the BOINC Data directory (C:\BOINC Data is a hidden directory only visible after temporarily setting "protected system folders visible" in "folder options" of the browser):

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I was surprised about perfect working of the new cooling arrangement: GPU temperature of GPX 640 not higher than 70 degrees Celsius, and 56 degrees for the neighboring GPX 750 Ti ! I tried to overclock the GPU 640 but after rising GPU / Memory clock 10% (benefit on WUs was marginal) GPU processing was instable. So I decided for the default values (some WUs with validation error through the night, sorry).

Conclusion
With running 2 Parks cuda55 tasks each the two graphics cards are finishing the GPU-WUs at about the same time (about 3:30 h). For the GTX 750 Ti I expected a bit a better throughput of WU's as now established, but I know it is difficult to make a forecast comparing the specs of the two graphics cards. For proper cooling I have to care that airflow outside of the tower does not build a "short circuit": Warm air from the rear must not flow to the side where the big fan takes in fresh air).

Next step: I will try to run the two GTX 560 Ti and the two GTX 670 with the same cooling arrangement (informing later on).