Cool PC

A while back, I built a home PC with the latest and greatest top o’line graphics card, the nVidia GeForce 8800GTX. This monster was longer than your typical PC card,  took two slots and had two independent power connectors to feed it. It was an impressive piece of graphics processing until I got to Rivendell in LOTRO. Then, fwoomp, the dreaded blue screen of death (BSOD). 

This BSOD also occured under other programs that made heavy use of the graphics engine. I did the usual updating of drivers, ran dxdiag and searched the web but all was too new. The computer wasn't overclocked and had worked well with other graphics cards. I RMAed the card but same thing happened again. What I did notice was the card ran hot, to hot to the touch. I remember Nelson Pass of Pass labs writing that a good rule of thumb was if it is too hot to touch, its more than 60°C. So I measured it with an IR remote thermometer and saw temperatures in excess of 80°C. I installed the Microsoft debug tools and found the crashes were occurring in accesses to video memory. The video memory was thermally connected through the heat sink to the GPU and my theory was the GPU was heating the memory and causing it to fail.

I tried to solve it with more fans except it's own fan housing limited how much airflow I could get across the heat sink. Many of the manufacturers were bringing out 8800GTX with built in water blocks. Microelectronics and liquids in the same case seemed like a bad idea, but I was running out of options in salvaging my graphics card. 

First item was a new case that could hold the radiator, pump and reservoir. I went with the Silverstone TJ07 full tower case with a clear side window. This was inspired by a beautiful system made by Puget Systems. This is a well-made expensive case and was \*almost\* made for water-cooling.

 

I went with the 3/8” ID tubing and the following hardware:

  • Danger Den 8800GTX water block
  • Koolance Socket 775 water block
  • Danger Den Delrin fillport
  • Black Ice Radiator with dual Scythe SFF21E fans
  • Swiftech MCP355 with pump mod
  • Aqua Computer Reservoir

The system was hooked up this way. I had the reservoir backlit with a blue LED and it had a temperature sensor. 

The TJ07 has a top screen for two exhaust fans. Keith and I modified the screen to hold the radiator with pop rivets and the Scythe fans were mounted to the radiator using rubber fan mounts.

 

I drilled one hole in the top for the fill plug. It was a tight fit with the mother board. 

The Swiftech pump was mounted in the bottom behind the power supply.  Originally it was mounted with the enclosed block of double stick foam, but it was loud and sounded like an aquarium pump. A better solution was to use a pair of urethane cylindrical mounts. These are very soft and highly damped rubber mounts. The pump entry line was braced with another standoff to add stability for the pump. This reduced the pump noise considerably.

 

Each water block came with instructions for removal of the existing heatsink and replacement with the water block. I cleaned up the existing heat sink material and spread the included thermal compound with a business card. The boards are put into the case and hoses cut to size and attached to the fittings with o-clamps. I found the fittings that do not capture the o-ring could be easily over tightened and distorted. There is little margin between over- and under- tightening.

I originally used Tygon R3603 tubing. It’s thick-walled, doesn’t kink but it became stiff and brittle over time. I used vinyl tubing from the hardware store and it has worked fine. I tried one of the non-conductive liquid coolants but it built up goo in the tubing and made a mess of things. I had to flush the system and switched to distilled water.

Another thing that came in handy was a combination of the UV lights with a few drops of “Dye-Lite” leak detection dye in the fluid. At first, this was to make it look cool but is very effective for spotting leaks.

I tried a flow meter that was based on a little turbine; however, the shaft seized from the fluid. The turbulence of the fluid in the front panel reservoir window is enough to show flow.

Once the system is put together, This is a closed system and the air in the reservoir needs a way to get out for the fluid to get in. This can be done by running a small plastic into fill port until it reaches the reservoir.  Once it has some liquid in the system, I apply power to the pump for a short period of time and start working the air out of the lines. I repeat this process until the system has no more air in the lines and then check for leaks. Once this is complete, the pump is hooked to the 12V power and the system closed up.

Since I’ve installed the liquid cooling system, I have never seen the BSOD again and the graphics card has been well behaved.  The GPU and CPU temperatures range from 30°C to 38°C and runs remarkably quiet. It has had on occasion, minor leaks from fittings which were either too tight or had worked loose. It also will leak if the hose becomes too old and stiff. 

 

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