Friday 15 July 2016

Air Flow: Improving Cooling in My Gaming PC, Part 1

It's been a couple of months since I built my computer, and recently I decided that I wasn't quite finished with it yet. I had just finished playing Uncharted 4, not quite ready to jump into a big commitment like the new Witcher 3 DLC, and I wanted to test out what the new rig could do. As it so happened, one of my friends had gifted me the new Mad Max game on Steam, so I decided to see how well UNICORN-31 coped when confronted with a triple-A video game not yet a year old.

The answer, it turns out, was not well. The game would run fine for about 60 seconds and then start to get awful frame-rate drops that made the game feel like it was running in slow motion! I tried fiddling with the graphics settings for a while but even on the lowest this still happened. I read up about it online, found a number of people with similar problems who all recommended different things, none of which worked for me, and decided that this was why PC games tend to be cheaper than console ones: sometimes your specific hardware setup is going to clash with the way the game is made and not work perfectly.

I moved on to another game, Divinity: Original Sin, which I've owned for a while and wanted to try out, especially since they released a free 'enhanced edition' upgrade some time last year. Things initially seemed good, the gorgeous 3D title screen running at a smooth 60fps. But once again, when in-game, things began to chug after a couple of minutes. Divinity doesn't have nearly so many knobs and sliders in its graphics options, but after trying a couple of variations I was still getting the same problem. From what I read online, my conclusion was that I had a problem with cooling: when first starting a game when the graphics card and CPU were cool everything was running smoothly, but as soon as things began to heat up inside the case performance would drop significantly. The message was clear: I needed to improve cooling inside my computer! 

One of the things I've learned at my time at Facebook is that if you're going to undertake a project, it's important to be able to measure its success. So the first thing I did was take advantage of the Steam sale and buy 3DMark, an application used to benchmark the performance of gaming PCs. It offers a few different functions, including a benchmark suite which renders various graphically intense scenarios and measures how well the system handles them, and a stress test in which it plays the same loop over and over again to show if system performance degrades over time. The results were much worse than expected: the benchmark ran around 10fps, and the stress test showed a stability of only 12% in framerate! I opened up the case and assessed my options.

The first thing that occurred to me was the position of the hard drives. Hard drive bays are always located towards the front lower part of a computer case, which means that they tend to be right in front of the main input fans. When building the computer I put my solid-state drive (SSD) in a lower slot and the hard-disc drive (HDD) above it (see picture), because I knew that platter-based hard drives actually create heat whereas solid-state drives do not and thus it would make more sense for the HDD to be in a more direct air-flow. I also left a gap between them because it matched up with the spacing of the plugs on the power cable. As a result, the bulky hard-drive was blocking one of the fans providing air-flow into the case! A quick swap relegated it to the bottom of the case and put the much smaller solid-state drive in the slot directly above it, meaning that the two input fans were now much less obstructed.

The second thing I looked at was the positioning of the video card. I had it mounted in the top-most PCI-slot, which meant that there was about a 2cm clearance between the top of the card and the CPU cooling tower. The GPU has a pair of built-in fans on the underside which blow air upwards into the heat-sink, which cools the underside of the card nicely. My thought was that with the top of the card so close to the cooling tower and with relatively little air blowing across it this side of the card might be getting too hot. So, I moved the GPU to the bottom PCI-slot, so that the top of the card would get more air blowing over it.

After closing up the case and running the stress test again, I was pleased to find that the stability was now 92% (the benchmark was still pretty low, but it's designed for much higher-end GPUs). Whilst that's a huge improvement over what was happening before, it's still not a pass according to 3DMark. There was still work to be done!

I decided that now was the time to actually make the effort to sort out the huge bundle of cables going through the middle of my computer case. As you can see from the picture, they form a trunk about 3cm in diameter at the widest point which can't help the air flowing from the front of the case. It's a bit hard to see but I also have the power cable for the CPU running diagonally from the bottom centre (where it comes out of the power supply) to the top left (where it plugs into the motherboard) because that's the only way the cable would reach! As a result, it touches both the GPU and the cooling tower, which doesn't seem like a good idea!

Look out for Part 2 where I'll talk about what I did to tidy up my cables, as well as add a bit more control to the flow of air through the case!

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