Superquiet Superclocked DIY Core 2 Duo System

Do-It-Yourself Systems
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OVERCLOCKING THE SYSTEM

The Conroe family is very overclock-friendly, as are the new motherboards and memories. Reports of overclocks of 50% or more are not uncommon on the enthusiast forums.

The latest generation of CPUs require new test and stress software. Older programs such as CPU Burnin, CPUburn, and Prime95 do not load the CPU fully. The new gold standard for CPU, north bridge and memory stability is ORTHOS, which runs two copies of Prime95 with varying parameters, while the best CPU load program for Core 2 or Core CPUs is TAT (Thermal Analysis Tool), which is a proprietary Intel program that can be downloaded through links in this thread. The best video card stress tools continue to be rthdribl and ATI Tool. ATI Tool works with both ATI and nVidia GPUs, and consumes slightly more power in tumbling block mode than in artifact check mode.

Running TAT at 100% on both CPUs, the core temperature of the E6600 at stock frequency and voltage (2.400 GHz and 1.35V) goes up to only 68C with the Ninja fan running at just 600 RPM. If you're not overclocking this CPU, you really don't need the kind of cooling described above. However, since my plan all along had been to overclock to the maximum frequency supported by quiet cooling, this temperature serves only as a comparison point.

I started my overclocking with the memory. The G.Skill HZ memory is hand-picked to support high clock rates and low latencies at elevated voltages. The highest reliable frequency I found for this motherboard and memory was 740 MHz 3-3-3-12 at 2.3V, or 812 MHz 4-4-4-12 at 2.4V. As usual, the memory is not the limiting factor in my system clocking.

Initially, I had a week 24 CPU (the first week of production), which required a relatively high Vcore to overclock. My initial target for fan speeds was 700 RPM, which is very quiet but still audible. I was able to overclock to 3.244 GHz, but only at rather low ambient temperatures.

Later I got a week 28 CPU, which overclocks well at noticeably lower voltages. With this newer CPU, I was able to run the system with FSB and DRAM frequencies of 361 and 722 MHz, and DRAM, CPU and north bridge voltages of 2.30, 1.4625 and 1.55. The DRAM parameters were set to 3-3-3-12-5, and C1 Enhanced, SpeedStep and Hyper Path 3 were disabled. This ran the CPU at 3.252 GHz, and was completely stable with the fans running at only 600 RPM.

Getting the last few drops of performance required adjusting the tRD memory parameter. This parameter is not user-settable in the BIOS, which silently sets it to 5 when the other parameters are 1:1 and 3-3-3-12-5. Changing it to 6 with memset 3.0 made my system stable with FSB and DRAM clocks of 370 and 740. This runs the CPU at 3.333 GHz. To achieve complete stability, I had to overvolt the DRAM, CPU and north bridge to 2.30, 1.50 and 1.55 volts. Higher overclocks are possible, but only with faster fan settings. I was so pleased with the inaudibility of 600 RPM that I decided to stick with that.

Recent versions of the BIOS disable CPU auto throttling (called thermal control in the user interface) by default. If you want your CPU to last very long, it is imperative that you enable this feature in the BIOS, or that you always run RMClock to provide throttling. I let the BIOS control it.

eVGA sells many variants of the 7900GT video card. The N567 7900 KO SC (KnockOut SuperClocked) is overclocked at the factory to run the GPU and GRAM at 580 and 790 MHz. As with any nVidia card, to display or modify this clocking, you must install the CoolBits registry hack, available here. To achieve this clock rate, the GPU is overvolted from 1.2V to 1.4V when running 3D applications, which causes it to consume much more power than a standard 7900GT. After several experiments I was able to increase this overclock only slightly; in the end, I reverted to the factory settings.

I ran a bunch of benchmarks to compare my final overclock with the stock CPU and memory settings, and also, as much as possible, to my old 830D system.

Benchmark
Stock E6600 OC E6600 OC 830D
FSB, DRAM, CPU clocks
267, 333, 2.404
370, 740, 3.333
235, 627, 3.532
Video GPU, DRAM clocks
580, 790 (1580)
580, 790 (1580)
427, 555 (1110)
DRAM latencies
5-5-5-12-9
3-3-3-12-5
4-4-4-12-4
Sandra iSSE, fpSSE
132345, 71415
184027, 99278
35260, 40143 est
Sandra RAM bandwidth: int, fp
5204, 5215
7214, 7226
5820 est
Sandra memory latency
90 ns
61 ns
-
3DMark05, 3DMark06
10134, 5609
10406, 5911
5379, -
PCMark04 CPU, memory, graphics, disk
-
-, -, 11273, 12307, 4830
6999, 5569, 6795, 4372
PCMark05 CPU, memory, graphics, disk
6082, 5165, 8283, 4246
8472, 7249, 9104, 4256
-
PCMark04, PCMark05 system
-, 6580
-, 8180
7114, -

This system is very quick. Note the outstanding SSE scores; this system encodes video over three times faster than my old one. Its video FPS rate is nearly twice as fast.

FINALLY, SETTING FAN SPEEDS

As hinted many times above, I run my fans very slowly.

The Ninja is a truly exceptional heat sink. Even with the CPU consuming 100W at this extreme overclock, and the fan spinning at an inaudible 600 RPM, the cores stay well below throttling under my heaviest realistic workload (video recoding plus protein folding). This workload corresponds to 75% loading in TAT. With faster fan settings it is possible to avoid throttling even under the synthetic workloads, but I stuck with 600 RPM since it was all I needed. Because various programs report throttling temperatures varying from 83C to 97C, I can't say with any precision what my actual CPU temperature is.

The Condor cools the GPU very well, needing only a slight draft to shed its heat. I ran a series of fan speed tests loading the GPU with the ATI Tool artifact scanner. This provides a higher load than any game I'm aware of, though slightly less load than rthdribl. I used SpeedFan to adjust the voltage to the Nexus fan installed in the video chamber, and measured both the GPU and south bridge steady-state temperatures. The ambient temperature was 22C.

Nexus 120 Fan in Video Card Chamber
SpeedFan %
44
50
55
60
65
70
75
80
Fan RPM
598
670
721
774
830
870
917
970
GPU - °C
105
104
98
94
94
92
89
88
SB - °C
43
43
41
40
39
39
38
37

The fan becomes barely audible at about 650 RPM, although it is very quiet by most people's standards even at 1000 RPM. In this setup, there is no reason to run the fan faster than about 750 RPM. The default throttling temperature for this GPU is 130C, so none of the temperatures here are particularly excessive.

Nonetheless, in order to keep the GPU below 100C, I ultimately decided to let the fan run faster under load. I set SpeedFan to use a minimum of 44%, a maximum of 55%, and a desired south bridge temperature of 42C. The only time the fan speeds up is during benchmarks.

The P5W DH has five fan headers: CPU, CHA1, CHA2, PWR1 and PWR2. As the naming implies, these form three groups from SpeedFan's perspective: CPU, CHA and PWR. I used one of the PWR headers to control the top case fan, and the two CHA headers to control the video and power supply/hard disk fans. The top case fan and the power supply fan have NMT-3 controllers; these work well in combination with SpeedFan and slow these fans even more when temperatures are low.

I set the CPU fan to 43%, the top case fan to 44%, and the video and PS/HD fan to 44-55% depending on the MB temperature. When the ambient is 22C and I'm folding, the fans run at 580, 590, 590 and 480 RPM. They speed up a bit when the room is warmer, typically 20 RPM. The hard disks stay below 40C, and the power supply fan never spins up.

How quiet is this system? Well, if the DVD isn't spinning and the hard disks aren't seeking, the only perceptible sound is the faint hum of the LCD power supply echoing off the wall six feet away. Obviously the house and neighborhood must be totally quiet to hear this. By comparison, my company laptop is outrageously loud.

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Articles of Related Interest

Quiet DIY OC'ed Pentium D 830 System, Part Two
Quiet OC'ed Pentium D 830 System
Quiet PC for Torrid Thailand
Doug's Quiet Wood Case PC

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