Quiet DIY OC'ed Pentium D 830 System, Part Two

Do-It-Yourself Systems
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April 19, 2006 by Chris Thomson

Chris Thomson returns with Round Two of his Pentium D silencing saga. As in Quiet DIY OC'ed Pentium D 830 System, Part One, Chris does a great job with systematic documentation, and this time, he incorporates the feedback on his original DIY article from many forum members. By identifying names, their comments, and the way these comments were used for further improvements, the article also becomes a showcase of the SPCR spirit: A community sharing in exploration and discovery.

Readers who haven't read part one are encouraged to do so before plunging into the hot waters below. It'll be fun to go through the forum discussion, too, and then see what Chris has done with some of the suggestions.

Mike Chin, Editor

 

I first wrote about this system in Quiet DIY OC'ed Pentium D 830 System, Part One. That article ended with the system seriously overclocked, the case open, and cooling provided by four AcoustiFan DustProof fans running at 675, 685, 695 and 995 RPM, and aided by a couple of ducts.

Then the SPCR forum crowd weighed in. Brutal, but helpful. The comments in the forum launched me on another round of mods. The goal was to run with the case closed, preferably with even slower fans.

OVERCLOCKING OVERDONE

Before I started on those changes, I had issues with system stability.

I had been running the system with the FSB/DRAM at 240/640 MHz, the GPU/GRAM at 427/1110 MHz, and the DRAM/CPU/MCH at 2.00/1.325/1.60 Volts. It could run Prime95, CPUBurn, protein folding or PCMark/3DMark indefinitely, but had occasional odd hangs or slowness running HD- or CD-intensive tasks. The behavior was consistent with lost IDE interrupts. I tried dialing back the clocks a bit and these symptoms disappeared. This led me to conclude that the performance limit in my system is set by the chipset (north and south bridges), not by the CPU or memory.

After some experiments, I settled on FSB/DRAM and GPU/GRAM speeds of 235/627 and 427/1110 MHz. At these speeds, I was able to reduce the DRAM/CPU/MCH voltages to 2.00/1.30/1.55. The CPU voltage and clock reductions dropped its power consumption by 6%, which made the VRM run cooler. CPU-Z reports the CPU clock as 3.532 GHz.

BETTER VRM AIRFLOW WITH A BAFFLE

Rereading my article and looking at the initial responses led me to the question: How can I increase the airflow over the VRM?

My earlier thinking had fruitlessly focused on upstream deflectors. What if I added a downstream baffle that would force more air across the VRM?

This led me to the idea of a baffle that would force all the top case fan air flow over the VRM parts by sealing off the other paths. A simple right-angle baffle that mated with the Ninja duct would do this: the top flap of the Ninja duct ends 2 inches from the motherboard, so a baffle that mated with the top and front edges of the Ninja duct would force all airflow to the top fan to come from the VRM region of the motherboard. Here is what the baffle looked like before installation

VRM baffle before installation
Simple VRM baffle, before installation (front view).

and after installation

The VRM baffle installed in the system
VRM baffle installed in the system.

The baffle is held in place by a couple of cuts into the near top and near back foam, and by the CPU fan. It sits snugly on top of the Ninja duct. To reduce noise, I added some 5mm foam to the inside edges of the baffle, as well as the top flap of the Ninja duct.

This worked quite well: the exit air temperature at the far edge of the top case fan dropped 1°C, and the VRM components seemed to be a lot cooler, although they were still very hot.



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