XPS 8930, How I Fixed the Noise Issues

I recently bought a Dell XPS 8930 with an i7-8700 (not 8700k). When the CPU is under heavy load (i.e. around 100%) the case fan and the CPU cooler fan really ramp up and are very loud. When under heavy load the XPS 8930 is the noisiest computer that I have ever used. When you are not stressing the CPU though, it is pretty quiet.

I have found two solutions to this issue:

(1) Replace the CPU cooler with a more effective one - not easy but very effective

To me it seemed that the stock CPU cooler - which is quite a small unit - was struggling to keep the CPU cool when the CPU was running at 100%. The CPU temperature when at 100% for a period of time was typically in the high 80's Centigrade and peaked in the low 90's. The issue with the Dell case design is that there is only around 70mm of space from the top of the CPU to the side of the PSU. The stock CPU cooler and fan is 50mm high and has an 80mm wide fan. There are not many CPU coolers that will fit within 70mm and still have space for airflow. For example, one of the best "low profile" CPU coolers is the Raijintek Pallas. However, this is 68mm high. I wasn't confident that the fan would work very well if it had a flat surface just a couple of millimeters above it. In the end the fan that I found that did fit and was effective was a Scythe Big Shuriken 2. 

This unit is 58mm high including the fan - so still has 12mm/ half an inch of clearance. This CPU cooler is much larger with a 120mm fan vs the 80mm fan of the stock cooler. (So the surface area of the fan and heat sink cooler is more than twice that of the stock cooler.) The design also ensures that the heatsink clears the capacitors/resisters and memory banks that are close to the CPU. This CPU cooler doesn't seem to have to work very hard to keep the CPU cool even when the CPU usage is 100%. Under load my maximum CPU temperatures are about 5C lower than they were before and the fan noise from the Big Shuriken 2 is very low. Keeping the CPU cooler seems to mean that the case fan doesn't have to ramp up as much so that is much quieter too. I notice that the Big Shuriken also seems to have extra cooling capacity. Occasionally when the temperatures are high you will hear the CPU cooler fan ramping up a bit (though still much quieter than the stock cooler) and in a few seconds the temperature will fall from being in the 80's to being in the 60's and the CPU fan will slow down again. The stock cooler on the other hand simply seems to have to work at 100% all the time when the CPU is under load.

Changing the CPU Cooler isn't for the faint hearted.

Socket Clamp Backplate Issue - The CPU is held in place with a socket clamp - normally this screws into a backplate on the underside of the motherboard like this - it is the plate with three screws in it. 

All CPU coolers are held in place with another back plate that also fits under the motherboard and usually goes over the top of the CPU socket backplate. This is what the screws from the CPU cooler fit into. Motherboards have holes for these screws to pass through.  

Unfortunately Dell use a single back plate that has screw holes for both the CPU socket clamp and the heat sink. This is unusual and stops you using the back plate that comes with the CPU cooler.

You can replace the Dell combined backplate with a normal CPU socket clamp bacck plate and then use the CPU cooler backplate. This is what I did - I bought a brocken 1151 motherboard for £15 and took the (normal) socket clamp back plate off of that. (I could not find anywhere that sold just a socket clamp back plate - or even a whole socket clamp assembly.

Alternatively you could try resusing the Dell combined backlate instead of the CPU cooler backplate. However, I found that the existing screw holes in the dell back plate where the stock CPU cooler screws into were too small. You can get around this by knocking the screw holes out of the backplate with a hole punch but i didnt want to do that.

So for me step 1 was to get a socket 1151 CPU clamp backplate.

Then you can unplug everything from the motherboard. Before you do this take a few pictures of all the cables in place just in case you cnanot remember where they go. 

Remove the screws holding in the motherboard (7 of these I think) and remove the motherboard from the case. This is a pain because the case has absolutely no spare space around the motherboard and you have to get it to an angle to get it out so that the USB sockets etc dont catch on the case. I really wish that Dell had made the case just a quarter of an inch bigger all the way around the motherboard.

Take off the existing CPU cooler and the socket clamp so that you can remove Dell's combined back plate. Put the CPU somewhere safe. Put the socket clamp back on using your new socket backplate. Put the CPU back in. Then fit the new CPU cooler - making sure that you clean off the old thermal paste and use some new good quality paste. It really helps if you have a spare set of hands while attaching the CPU cooler - it would be really hard to hold the cooler in place on the CPU and screw it into place from the underside of the motherboard otherwise.

Then put it all back together and you should have a nice and quiet PC.

I did have one moment of panic after I put it all back together - as the system would not power up! I could not see any cables that were not back in the right place. Going back tothe photos showed me that I had missed a small cable that appeared to be for the power button. It had been pushed out of the way when trying to get the motherboard back in the case and was small enough to be hidden by other cables. 

(2) Reduce the Maximum CPU frequency - easy to do and effective

More details on this option are here:

Reducing CPU Maximum Frequency

Personally I found that a setting of 3900MHz made the XPS 8930 pretty quiet while having no significant impact on performance. In practice this isn't very surprising. In theory the i7-8700 can go up to 4600MHz with Turbo Boost. However, with longer running tasks the maximum CPU frequency rarely goes above 4000MHz.

Some people have recommended reducing the CPU Maximum State (in power settings) instead. Do NOT do this. If you set this to even 99% you will lose about 25% of your maximum CPU performance. I tested ripping a 2 minute section of a blu-ray. With Max CPU State at 100% it took 60 seconds - with a setting of 99% it took 76 seconds. This big change in performance is because even a setting of 99% disables all turbo boosting of the CPU so the maximum CPU frequency falls from 4.6GHz to 3.2GHz. On the plus side though - if you are willing to take this significant hit in performance then your PC will be very quiet.