Quiet MP Dual-CPU Workstation

Do-It-Yourself Systems
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4) Provide Cooler Air for the PSU

The vent slots on the intake side of the PSU seem too bulky. I felt they could be more open to allow better air intake, so a pair of needle noise pliers were used to twist them 90 degrees, substantially increasing the air gap between each metal slot.

Then I decided to provide a path for fresh air to come in from the top front of the case directly to the PSU intake vents. I did this with the hope that the case inside would stay cooler which would help the CPUs, the hard drive and other components such as the voltage regulators. An AMD system builder guide states that the front vents of a PSU can rob the HSFs of cool air, thereby preventing them from cooling to their full capacity. A tunnel was made with foam and stiff paper. This is visible in the photo above as well as the one below. It is marked #3 in the photo below.

5) Case Door Mods

The new PSU intake duct required a larger intake vent in the front of the case. So...

Although the Antec case has some ventilation holes that appear to be designed in around the edges of the front behind the hinged door, the intake air tunnel seemed a bit silly without a larger opening. So the top of the plastic door was cut open as shown in #1 above. A lip that reduced air intake on the bottom of the door, #2, was also cut away.

Later, I created a rubber sound-damping gasket, marked #4, that presses up against the optical drives to reduce their noise when accessed. Note the recessed notches cut into the rubber piece to prevent the door open buttons from being pressed when the case door is closed.

6) Quiet the Hard Drives (and other mods)

I next underwent a long process of experimentation to quiet my hard drives. I tried several materials and used multiple configurations, but only my final attempt gave me the best performance acoustically and thermally. Only the noteworthy versions are reviewed here. There were a few other... aborts.

VERSION 1: camera foam, 1" thick, "taco" w/sidesinks. Good acoustic performance, but poor thermal characteristics and case fitting issues

I built a foam structure in the shape of a taco. Each hard drive was covered in foam on the top, bottom and front. Side heatsinks were made from doubled U-channel aluminum pieces and screwed tightly to the sides of each hard drive. This is the cooling concept presented in the SPCR article Effective Passive Hard Drive Cooling.

Sorry for the blurry photo. It really is 2 drives covered in foam and equipped with side heatsinks.

V1: Camera foam HDD sandwich
dBA
ChangeB
ChangeP
Front of case (0.5" from case at HDD height)
52
-10
-6
Hard drives (inside case between 2 hard drives)
55
-15
-5
Exhaust fans (outside case, corner closest to fans)
56
-13
-8
CPU fans (between sides of 2 CPU fans)
61
-8
-2
Temperature
C
ChangeB
ChangeP
CPU 0/CPU 1 (with BurnK7)
64 / 59
+13 / +11
-2 / -2
40GB/80GB HD (Dtemp)
~56C
+18~22
NA

*ChangeB = Change from Baseline; ChangeP = Change from Previous

This mod was a minor success. Even though the drives were not in perfect suspension, idle noise dropped to the point where I could almost sleep at night, but temperatures shot up. Way up. So far up that I stayed awake at night worrying about my hard drives. How ironic! Maxtor states max. operational temp is 55C. Seek noise was terrible with this setup. While the upper hard drive was okay, the lower hard drive made a huge racket.

VERSION 2: Vented 1" rebond foam pita pocket w/sidesinks & case hacking. Acoustic deadening better than V1, but even worse thermal performance

In this version, I constructed a foam enclosure that resembles a pita pocket using the densest rebond foam available at my nearby shop. This is much like the stuff used for carpet underlay. Not only were the tops, bottoms and fronts covered in foam, but also the sides. I tried to ensure adequate airflow by creating convection vents for the sidesinks. To fit the drives into my case, I had to remove the lower drive cage tray and suspend the pita pocket in a vertical orientation.

Before I took these measurements, I also added foam to the feet of the case to decouple it from the underlying surface.

V2: 1" rebond foam pita pocket w/sidesinks
dBA
ChangeB
ChangeP
Front of case (0.5" from case at HDD height)
<50
-12
-2
Hard drives (inside case between 2 hard drives)
<50
-20
-5
Exhaust fans (outside case, corner closest to fans)
<50
-19
-6
CPU fans (between sides of 2 CPU fans)
<50
-19
-9
Temperature
C
ChangeB
ChangeP
CPU 0/CPU 1 (with BurnK7)
68 / 61
+17 / +13
+4 / +2
40GB/80GB HD (Dtemp)
~66C
+28~32
+10

*ChangeB = Change from Baseline; ChangeP = Change from Previous

Although the measurements state otherwise, this setup actually sounded a wee bit louder than V1. There seemed to be more high-pitch whine coming through. I would have considered this a pretty good attempt, except that my hard drive temps were way, way over spec. Closing off the sides of the hard drives must have really choked the airflow. I stayed with this setup for a nerve-racking 2 days before I abandoned it.

VERSION 3: Backtrack to bare suspension, sidesinks, many other mods. Somewhat quieter than before quieting the hard drives

I was hoping to see the difference between a bare suspension and a sandwiched one, but I had an impatient streak and performed a whole bunch of modifications before I made any measurements. I did the following:

a) removed the lower exhaust case fan and replaced with filter
b) inverted the HS fans back to blow air onto the heatsinks
c) rerouted SCSI and floppy cables behind the motherboard for better case airflow
d) moved PCI cards down to make more space around video card

V3: Not-so-baseline bare suspension
dBA
ChangeB
ChangeP
Front of case (0.5" from case at HDD height)
54
-8
+4
Hard drives (inside case between 2 hard drives)
60
-10
+10
Exhaust fans (outside case, corner closest to fans)
50
-19
0
CPU fans (between sides of 2 cpu fans)
54
-15
+4
Temperature
C
ChangeB
ChangeP
CPU 0/CPU 1 (with BurnK7)
69 / 65
+18 / +17
+1 / +4
40GB/80GB HD (Dtemp)
45 / 49
+7 / +15
-17~21

*ChangeB = Change from Baseline; ChangeP = Change from Previous

The bare suspension revealed no surprises. Noise levels increased, but the heat decreased.

VERSION 4: 1" rebond foam club sandwich and PSU ducting mod. Acoustic performance comparable to V1 with thermal performance that's just barely acceptable

Here, I modified the pita pocket from V2 by detaching the side pieces of foam from the pocket and instead attaching them to the sides of the case. Between the hard drive was a 1/2" piece of EVA foam.

I obtained the following results:

V4: 1" rebond foam club sandwich + PSU ducting
dBA
ChangeB
ChangeP
Front of case (0.5" from case at HDD height)
50
-12
-4
Hard drives (inside case between 2 hard drives)
50
-20
-10
Exhaust fans (outside case, corner closest to fans)
50
-19
0
CPU fans (between sides of 2 cpu fans)
53
-15
-1
Temperature
C
ChangeB
ChangeP
CPU 0/CPU 1 (with BurnK7)
66 / 58
+14 / +10
-4 / -7
40GB/80GB HD (Dtemp)
55 / 55
+7 / +15
+10 / +6

*ChangeB = Change from Baseline; ChangeP = Change from Previous

I can report that my rig sounds about as quiet as it did in version 1. But HDD temps were too high.



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