Saturday, March 17, 2018

Airflow (a new PC build in an old case)

Let me start by saying I do NOT like to build my own PC. Once upon a time, long, long ago, I considered it fun. These days I just may build one myself for cost reasons.

Regardless if you use a new or an old case (as I did) it still is a good idea to pay attention to the airflow in your case...


Goodbye Intel, welcome AMD.

When my trustworthy Dell XPS710 gave up on me (after ten years of reliable service and starring in a major role in Tabula Rasa). Reboots were becoming complicated affairs, and spontaneous crashes didn't help much either. Time for something new.

Except for the AMD64 I've been always on Intel's side, but this time I opted for an AMD build.

  • Ryzen 5 1600X
  • Scythe Mugen 5b cooler (single fan version)
  • Asrock AB350 Pro4 mainboard
  • Corsair 2400 memory
  • Seasonic 550W Focus Gold
  • Arctic Freeze PWM120 DST fans
  • Gigabyte Geforce GTX1060 Windforce
  • Akasa USB3 card reader (review)

HDD, SSD, DVD ROM and case were leftovers. This isn't the cheapest configuration, but it isn't a high end gaming machine either. The 1060 is an afterthought, and perhaps overkill.


A more economic build

Honestly, you could save a lot of money with a more economical build, with pretty much the same performance...
  • Ryzen 5 1600 or 1500X, which includes a boxed cooler
  • Geforce GTX1050 or GTX1050 TI

Unless you go for 32 GB you're probably best served with 16 GB of 2600 memory, but check the mainboard documentation and the internet what works and what doesn't...


Old case

I had an old case laying around (10+ years I think, Piano black paint, completely perforated front with way too many 5.25 drive slots) and decided to re-use that one.

I had three reasons to still use an old style case..
  1. I already owned it
  2. I was trying to save some money
  3. Principle of the thing (this case has been gathering dust for years and was actually never used)

Layout

This case handles an ATX board. At first glance there's a lot of space (and after mounting there's still a lot of empty space left) but the connectors on the mainboard made things a little complicated, so did the length and the 'silent' mode of the video card.



 
The front of the case is mostly perforated drive bays. On the back there's a small perforated area and a slot for a fan (3).

There are two large vents on the side and one on the back. I don't like to mount fans on the side panel, as they will hamper taking off the side panel, as well as making it harder to predict which route the air takes.

My home server just uses the PSU fan and a single (temperature controlled) fan on the backside, and in that machine I used a piece of tape to close these side vents:


This time I kept the side vents open.


The basic idea: push a little more than I pull
By putting two pushing fans on the front and only one pulling on the back I push a little bit more air into the machine than I pull out. All surplus air is leaving the case through back and side vents, or at least that's the idea.



PSU fan

The PSU (5) has a 'silent' mode. If consumed power is at a minimal, the fan falls totally silent. To make sure the power supply isn't heated up by CPU (9) heat there's that extra fan (3) on the case to move air out before it reaches the PSU.


CPU cooler

The big CPU cooler, a Scythe Mugen 5b, just fits. It has a single, low speed fan (4).


Case fans

I mounted three Frozen Arctic PWM120 fans. The two on the front (1) (2) are mounted on two Lian Li drive cages I still had laying around. These things are intended to mount four 3.5" disks in three 5.25" drive slots. I didn't need that many drive slots, but they allowed me to mount some fans in the front. Newer cases typically have fans there. (Again, this is an old case.)

All fans are mounted using rubber pieces.

The two fans on the front pushing air into the case, the air flowing over the hard drives towards the video card and CPU cooler.


The third is mounted on the backside, sucking out any hot air coming from the CPU cooler. (Note that I also added two few perforated slot panels next to the video card bracket (8). More about that later.)


The mainboard has three chassis fan connectors (some websites claim two, but there are actually three). These Frozen Arctic fans have a special, stackable connector and use very little power, so you can connect two to three fans to a single controller. In this case each fan got its own controller.


According to the documentation these Frozen Arctic fans should run at 500 RPM at PWM 0%, but in reality they behaves erratic at PWM's below 20%, and run a bit faster than suggested by the diagram.


Bios fan settings

I first installed HWInfo64 to check on the temperature sensors, then went into the Bios and set all CPU and chassis fans to 'silent' mode. Then I tested the system with no, little, and maximal load. (I generated maximal load with a combination of Prime95, Furmark and Heaven.)

Then I played around with the fan settings, increasing them until I found the temperature that I wanted under full load.



Finally, I tried to tie fan speed to mainboard and CPU temperature. Unfortunately I couldn't use the mainboard temperature sensor as the steps in the settings were too large, so I had to use CPU temperature readings.

I then used the same settings for all the fans.
  • T1 - 34 C - 20%
  • T2 - 40 C - 40%
  • T3 - 47 C - 60%
  • T4 - 53 C - 80%
  • T5 - 60 C - 100%

With these settings the case fans (1) (2) (3) were running at 770 RPM with the machine idling.


Gigabyte GTX1060 Windforce 'silent mode'

When the GTX1060 (7) has nothing to do its fans fall silent. I noticed that those fans were starting and stopping now and again, even with very little use. Apparently some heat would build up which would be enough to start and stop the video card fans.

I played a little with the front fan speeds, and by increasing the minimal speed of the lowest chassis fan (2) a little I kept the video card cold enough to leave the video card fans off.

Adjusted setting for the second chassis fan (2):
  • T1 - 34 C - 25%

With this the bottom fan ended up running 870 RPM with the machine idling. I may have to adjust this when summer arrives and environmental temperatures go up, but I hope to be able to keep the video card fans off even during the peak of summer. Let's see what happens.


Design flaw?

The Gigabyte design with its dual fans cools well and the card itself performs well, but it has a minor drawback. The aluminum cooling profile doesn't direct the airflow towards the backside of the card, out of the case (even though the card's bracket is perforated). In fact, half the hot air is directed towards the mainboard PCB, the other half just into the case.


So the fans on this video card do NOT push the heat out!

Which means you need case fans. But I was planning to use them anyway.

(And, of course, the battery on my mainboard is directly in the hot air stream. That is going to help.)

Here's an image of a GTX750. Here you can see that the cooling profile is properly aligned with the card. The shroud is still open towards the front of the case though, so you'd still need case fans, but it's better than heating up the PCB of the mainboard.


There are better designs where all air is pushed out of the backside bracket. If you can afford one, buy one of those.


Real world (cooling) performance
 
Typical use: running a torrent in the background, doing some browsing, playing some music:

  • Environment 20 C
  • MB 32 C
  • CPU 32 C - CPU fan 368 RPM
  • GPU 47 C - GPU fans 0 RPM
  • CH1 fan (1) 775 RPM
  • CH2 fan (2)  860 RPM
  • CH3 fan (3) 715 RPM
  • SSD 29 C
  • PSU fan 0 RPM

Playing a movie results in the same numbers. Guild Wars 2 (a light game) had the CPU at 37 and the GPU at 68.

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