Workstations: keeping it cool

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For CAD, workstation performance is essential, but keeping your machine cool without it sounding like a plane taking off, is also vital.

Summer has arrived and as I sit in my office complaining about the heat (us Brits love to talk about the weather) IÝm watching an older workstation gradually slow down as it struggles to exhaust the heat it produces (a bit like the way IÝm feeling in a non air-conditioned office). Time for a fan upgrade I think.

Just about every device in a computer produces heat ± a side effect of switching devices. The smaller the physical transistors are the less heat they produce and the less power they consume. Modern chips are measured in the size of their production process in nm (nanometres). Smaller switches = less heat and better performance. The current smallest fabrication produces 65nm. As performance and functionality means packing more transistors onto a single chip (dual core, for instance, is packing two cores in one chip) even though the die is getting smaller the complexity is increasing. This relationship between smallest size, production of heat and wattage consumed has given Intel its new slogan ýperformance per watt¯ for the new Xeon processors. This might seem strange when all the design, analysis and CAD users want is ultimate performance but if you have a room full of racks to render images for films then your electricity bill becomes quite important to you as well as air con!

Cooling down

The heat that performance components produce – whether it is CPUs, GPUs or disk drives (mechanical heat producer) etc – has to go somewhere. The standard approach for CPUs and GPUs is to use a highly conductive material (generally metal based for obvious reasons) in a heat sink with air cooled fins backed up with electric fans. These little electric fans can be the cause of a lot of noise in older workstations, and this is something I often hear complaints about.

The primary purpose of a fan is heat removal by airflow. If a fan is physically small for packaging reasons then to get the required airflow they need to spin at a high rate, hence the noise. Today fans are designed to be more efficient by being physically larger and spinning slower, whilst still maintaining the required airflow. This airflow throughout the whole case is very important for the system. This is why all the OEMs (Original Equipment Manufacturers), such as Dell and HP, and the SIs (System Integrators), such as CAD2 and Xworks are designing and using special cases to exhaust the hot air. I was looking at the new 690 workstation from Dell the other day and it has separate compartments for CPUs, memory, hard disks and graphics to stop the heat transfer from different components. Likewise, HP uses a thermo fluids package when designing their workstations which models airflow throughout the whole case.

However, donÝt think that some of the smaller SIs canÝt deliver quiet systems. SIs have a greater choice of cases to choose from and can fit the latest heat sinks and fans. Some of the first designs for ýupside down cases¯ appeared in SI systems before OEMs even picked up on them. Originally fans ran at a constant speed but now they have a third wire to adjust the speed. Motherboards and CPUs have heat sensors on them which send signals to the fans. Often when you turn on a workstation the fans kick in at a high speed. This is just in case there has been a forced restart under a high load. Once the temperature sensors have kicked in and registered all is OK then the fanÝs speed will reduce to normal operation.

Reducing noise

So what can you do if your workstation sounds like a washing machine on a spin cycle? The first thing to do is take it apart and clean out any dust and fluff. If a machine gets clogged up then the fans will need to spin faster to clear the heat which results in more noise. If a fan fails then the other fans increase speed to compensate therefore increasing the total noise further. A lot of systems slow down their processorsÝ ýthrottle¯ if they get too hot and you might only know this as the system starts to slow down. Typical fan failures arise because of a stray power cable jamming into the fan blades ± which just goes to show you that a well put together workstation with cable control is important and may help prevent unnecessary stoppages.

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Once you have established there are no problems with the running of your fans and they are just noisy you could switch to a modern design with better bearings. They generally come in stock sizes 60mm, 80mm etc and a good source for these in the UK is www.overclockers.co.uk as they list the noise level for each model they sell. Likewise your CPU heat sink and fan design (generally integrated) could also be very noisy. If you have a dual CPU system your options are limited but for single (one or two cores) CPUs the Arctic Cooling range is quiet and very good value. Just make sure that you put a very thin and even heat transfer paste on the CPU when installing. These are also available from Overclockers.

The next stage in cooling is to use liquids commonly known as water cooling (not necessarily water!). Water cooling is generally used in specialist applications such as Cray supercomputers or for game players to get the fastest frames in certain games. This is basically a miniature domestic fridge piped to ýheat blocks¯ attached to the hot components. Armari sells a liquid that is non-conductive and can be poured onto live circuits. IÝm not suggesting that this is a solution for general workstations but Intel has adopted a similar technique by using heat pipes for its latest Xeon Processors. These have physical pipes filled with gas that takes the heat away to the cooling fins where the temperature drops and then drawn back to the hot area again.

Heat is one of the main factors for failures in computer components, when you sniff that electrical burning smell then itÝs already too late. If you suspect that your system canÝt survive the current heat wave I would shut it down and go down the pub for a long lunch! Anyway thatÝs the excuse IÝm using!

Robert Jamieson works for workstation graphics specialist, ATI.

rjamieson@ati.com

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