Superquiet Superclocked DIY Core 2 Duo System

Do-It-Yourself Systems
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COOLING THE CPU, NB & VRM: THE REALITY

It was a pretty good plan, and it would have worked if I hadn't given in to the dark side and started overclocking heavily. This required boosting the CPU core voltage, which in turn boosted the power consumption radically, into the vicinity of 100W. As with my old 830D, this much CPU wattage meant unacceptably loud fan speeds to obtain reasonable temperatures with an XP-120.

Since I already had in hand a Scythe Ninja heat sink and matching duct from my previous build, I switched to that heat sink, which I knew for certain could cool the CPU quietly. The Ninja is huge and efficient. Here is a photo from its SPCR review.

Scythe Ninja heat sink with fan attached
The Scythe Ninja tower heat sink, with a 120mm fan attached.

While running the CPU at high voltage, I noticed that the VRM was getting pretty warm, though not nearly as hot as on my old motherboard. Still, it was hot enough that the heat pipe to the north bridge was actually working backwards: it was transmitting heat toward the north bridge instead of away from it.

My stockpile of earlier experiments contained a Thermalright HR-05 tower north bridge heat sink, so I decided to try it instead of the stock heatsink/heatpipe/radiator thingie. This was not particularly easy because although the HR-05 comes with a clip designed for Intel-style hoops, it is designed for hoops on the northeast and southwest sides of the north bridge. For some bizarre reason, the P5W DH has provision for all four hoops but only has two of them populated: the northwest and southeast ones. Mounting the HR-05 required severe bending of the clip to reverse the angles, since I didn't want to take a soldering iron to this insanely expensive and hard-to-get motherboard.

When mounted as designed, the HR-05 can be rotated to various angles as needed. In my reversed orientation, the attachment clip bumped into the bottom fins, and prevented this rotation. To address this, I cut notches in the bottom two fins, as shown in this (very blurry) close-up photo.

notch in HR-05 to make room for attachment clip
Notches in the bottom fins of the HR-05 allow it to be rotated.

The HR-05, though billed as a passive heat sink, does need some airflow to cool an overclocked 975X. Also, since the Ninja is a tower heat sink, there is no downward airflow onto the VRM from its fan. Fortunately, the fan on the Ninja can be positioned so that it pushes some air between the Ninja and the motherboard, and also between the Ninja and the HR-05. To capture as much of this air as possible, I angled the HR-05 with respect to the Ninja. This close-up shows the fan and the two heat sinks.

close-up of CPU fan and HR-05
The CPU fan spills some air onto the angled HR-05 heat sink.

Because I planned to duct the CPU heat directly out the back, there needed to be a top case fan to cool the rest of the motherboard. To minimize noise, I wanted to soft-mount this fan, but the P180 case is not designed for soft-mounting a top case fan. The top fan mount has two screw holes at the back, but at the front instead of screw holes it has two bent metal tabs to hold the edge of the fan. I got around this by breaking off those tabs and drilling two new holes. This is easy, since this part of the case is plastic. Just use a fan as a drill guide. I soft-mounted the top fan with an AcoustiFan gasket. After cutting out the grill to reduce noise and mounting the fan, the P180 spoiler still fits in place, and looks like this:

P180 top spoiler installed on soft-mounted fan
The P180 top spoiler fits over the soft-mount screws to keep fingers and paws out.

Here is an inside view of the CPU and north bridge heat sinks installed, together with the CPU and top case fans.

Ninja and HR-05 installed, with CPU and case fans
Ninja CPU and HR-05 NB heat sinks installed, with CPU and top case fans.

When the CPU fan is positioned flush with the heat sink fin closest to the viewer in the photo above, it intrudes into the first DRAM slot. Since I have only two DIMMs, this is fine. I use the black connectors, which are farther from the CPU.

The sides of the Ninja line up very well with the case openings, making ducting of its exhaust air very simple. This was mandatory in my old configuration, and still worthwhile in my new one. The duct I use has four flat panels, two long and two short. The long panels seal the top and bottom sides of the Ninja and force the air out the back case opening, which is sealed with some foam strips (these also bear some of the weight of the Ninja, its fan, and the duct). You can see the foam strips on the left in the photo above. Here is what the finished Ninja duct looks like, as viewed from the back of the case.

Ninja air duct, rear view
Ninja duct (rear view), with its foam lining.

The back portion of the duct is lined with thin (4mm) foam. This is not neccessary with a slow fan, but when I first built this duct I was using pretty fast fan settings and wanted to absorb some fan noise. The duct slips over the Ninja and nestles in the foam strips at the back of the case, like this:

Ninja duct installed in system
Ninja duct installed in the system; air still gets to the HR-05.

Like all of my ducts, this one is made from styrene, a stiff plastic that is very easy to cut and glue. You can find a tutorial here (posted by a guy in my home town!).

The base of the Ninja (below its fins) stands two inches above the motherboard. My duct covers only the fins, so it is possible to force air between the duct and the motherboard, with the effect of cooling the VRM. The approach I use to do this is to pull air across the board with the top case fan. To direct this air flow properly, I built a two-panel baffle that mates with the Ninja duct and the case walls to seal off all other paths to the top case fan, as shown in this photo.

Top case fan baffle to improve VRM airflow
Baffle to force top case fan air flow across VRM.

Here is what it looks like installed, with its edges tucked into some foam. As you can see, the only way for air to get to the top case fan is from the area around the base of the Ninja. This cools the VRM.

VRM baffle and Ninja duct installed
VRM baffle installed, together with Ninja duct.

Because the Ninja and HR-05 are remarkably efficient, and the exhaust air is ducted directly out of the box, only the gentlest of breezes is needed to cool the CPU, north bridge, VRM and DRAM.

So with two fans, two monster heat sinks, and a couple of ducts, the top third of the system is take care of.



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