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For extreme overclocking of processors, characterized by extremely high values of clock frequencies, it is often necessary to increase the core supply voltage considerably. These processes are accompanied by exceedingly high heat emission. If the heat is never dispersed from the processor chip, the heat balance required for correct operation of the core will be disrupted. Furthermore, the
High temperatures of specific internal structures of the CPU chip limit the range of clock frequency growth. Besides this, high
A powerful and efficient cooling system can help to withstand some decay in semiconductors. Such a cooling system can ensure acceptable conditions for the processor operation, even in the course of extreme overclocking.
Under conditions of extreme overclocking, the heat emission of the processor is so high that heat balance based on air-cooling support becomes inadequate. Liquid-cooling systems based on water are also unable to solve this problem. Water has the highest heat capacity of the natural substances that
The inefficiency of traditional cooling
However, the value of heat flux, defined as the amount of heat passed per time unit, is proportional to the temperature gradient:
This means that the rate of heat transfer depends on the temperature difference between the heating zone and cooling zone. To ensure efficient cooling under conditions of extreme overclocking, it is best to use cryogenic temperatures at the surface of the cooled chip.
Normal ice can be used as cooling substance;
— the energy produced by a transition from a solid state to a liquid state — is rather high. This circumstance ensures that relatively little ice will be needed during experiments. However, its melting temperature is only 0°C (32°F), which doesn't ensure high values of heat flux. Ice can be used in experiments in the field of extreme overclocking, but it is
The best temperature parameters are characteristic for so-called dry ice, or solid-state carbon oxide. Its temperature of phase transition is -70°C (-94°F). This, compared to normal ice, ensures far better values of heat flux. However, for carbon oxide, the temperature of phase transition into the gaseous state is much lower than the melting temperature of normal ice. This means more dry ice will be required for extreme overclocking experiments.
Liquid nitrogen is a more
Specific features and experimental results in the field of extreme overclocking of processors are provided in the following sections.
(With the permission of http://www.overclockers.ru , a Russian-language Web site.)
Liquid nitrogen has become the
The use of liquid nitrogen required nonstandard facilities to play the role of processor
The cooling container could have been manufactured by soldering (from sheet copper), drilling (one piece of copper), or
A stannic (tin) solder has never been recommended for such purposes, because standard solders of this type form unstable
Therefore, the third method was chosen. Elements of the container were joined using
The dimensions of the cylindrical cooling container were chosen as
Height — 300 mm
Diameter — 50 mm
Thickness of bottom — 3 mm
This construction was installed on the processor and fastened using metal rods with
The process of fastening this cooling system was as follows:
The copper cooling container was installed on an Intel Pentium 4 processor.
Metal rods with the appropriate screws were screwed into the holes in the motherboard and were fastened with nuts.
From above, the container was pressed against the board using a plate of aluminum, which had a hole in the center and several holes for fastening rods at its sides.
The rods were set into the holes, and the entire construction was fastened with nuts screwed from above.
A funnel made of stainless
Figure 3.14: Cooling system for extreme processor overclocking (
Figure 3.15: Filling the cooling system with liquid nitrogen
After some time, a computer equipped with this cooling system
Ice crystals falling from the copper cooling container caused another serious problem. This problem was
As for the problem of water, it was solved by placing a sheet of foam rubber below the motherboard.
Figure 3.16: Ice-crystal layer on the copper cooling container
Figure 3.17: Motherboard covered with frost
Later, another method was found to help solve the problem of condensation. The basic idea of this method was as follows: The entire motherboard was covered evenly with liquid nitrogen. As a result, the entire motherboard was cooled below the freezing point of water, and ice caused significantly less harm to the motherboard.
These steps ensured stable operation of the system in the extreme overclocking mode of the processor. Of course, this could occur only if the cooling container contained liquid nitrogen and, consequently, if it ensured constant cooling of the processor.
Intel Celeron 1.8 GHz
Intel Pentium 4 2.2 GHz
Intel Pentium 4 2.4 GHz
Intel Pentium 4 2.53 GHz
VisionTek GeForce4 Ti4600
Windows XP Professional/2000 Professional SP1
Nvidia Detonator 29.42
Researchers had to abandon thermal paste. At the temperature of liquid nitrogen, it would freeze. As a result, the CPU surface would be covered with a layer of ice, which would decrease heat exchange considerably. The cooling container also would freeze to the processor's surface. Therefore, a long time would be required to replace the processor. Because of this, a cooling container often was installed on a heat-dissipating plate, the Integrated Heat Spreader (IHS) of Intel Celeron and Intel Pentium 4 processors, without thermal paste.
Figure 3.18: Frozen thermal paste on the heat-dissipating plate of the processor
Overclocking can be accomplished by increasing the FSB clock frequency while increasing the CPU core voltage (Vcore) to the maximum allowed by the motherboard. At a core voltage of 1.85 V, stable operation could be ensured at FSB frequencies to 140 MHz. This would result in a CPU frequency of 2,520 MHz (Fig. 3.19).
Figure 3.19: Parameters of Intel Celeron 1.8 GHz overclocked to 2,519.91 MHz
Several tests were performed for this mode. Test results obtained using SiSoftware Sandra are in Fig 3.20.
Figure 3.20: Results of testing the overclocked CPU using SiSoftware Sandra
Extreme overclocking of Intel Pentium 4 processors can be achieved by raising the FSB clock frequency at the core voltage of 1.85 V. As in the previous case, cooling was performed using liquid nitrogen. In the course of extreme overclocking, all CPU models exceeded the level of 3 GHz. The best result was achieved by the Intel Pentium 4 processor intended to run at 2.53 GHz. Being cooled by liquid nitrogen, this processor showed stable operation at a bus frequency of 185 MHz. Under conditions of the fixed
Figure 3.21: Parameters of Intel Pentium 4 2.53 GHz overclocked to the maximum frequency of 3,524.38 MHz
In experiments on extreme overclocking using liquid nitrogen
In extreme overclocking experiments, researchers used the Gigabyte 8INXP motherboard based on the Granite Bay (E7205) chipset. To achieve high results, the CPU core voltage was increased to 2.1 V. Because the motherboard doesn't support such voltage levels, the voltage was raised using its hardware modification.
Figure 3.22: Parameters of Intel Pentium 4 3.06 GHz overclocked to 4,599.85 MHz
This example can be used to partially predict the performance of future processors with a clock frequency of 4.6 GHz and a bus frequency of 800 MHz. Such frequencies can be achieved only by the Prescott core, which has 1 MB of L2 cache memory manufactured using 0.09-micrometer technology.
Note that Intel processors are not exceptions. A similar procedure of extreme overclocking is
Extreme overclocking of AMD processors in systems with liquid nitrogen cooling has its own specific features. AMD products have no heat-dissipating plate similar to IHS on Intel processors; therefore, with AMD products, there is a high risk of
Well-known overclocker YAO (see http://www.piopioshardware.com , a Chinese Web site) accomplished extreme overclocking of the AMD Athlon XP 1700+ processor by increasing the multiplier and EV6 processor bus.
The system operated at the following increased voltages:
CPU core voltage (Vcore)
North Bridge voltage (Vdd)
RAM modules supply voltage (Vdimm)
The processor was cooled using liquid nitrogen; for the North Bridge chip, water cooling was used.
AMD Athlon XP 1700+ (Marking = AXDA1700DLT3C JIUHB0309UPMW, clock frequency = 1,467 MHz, FSB frequency = 266 MHz, L2 cache = 256 KB, Vcore = 1.5 V)
Epox EP-8RDA+, Rev.1.1, BIOS 3305
A-Data DDR400, 256 MB, 2.79 V (3-2-2-2.5 1CMD) × 2
Albatron MX420 (GeForce4 MX420)
Quantum (20 GB, 7,200 rpm).
Power supply unit:
Nvidia nForce Driver 2.3, Nvidia Detonator 42.86
As a result, the processor was overclocked to the frequency of 3,107 MHz, at a multiplier raised to 13x and a system bus frequency increased to 239 MHz. The voltage at the North Bridge chip was increased to 1.92 V using the hardware modification of the motherboard. RAM voltage was raised to 2.79 V; the CPU core voltage reached 2.016 V.
Figure 3.23: Parameters of AMD Athlon XP 1700+ overclocked to 3,107.05 MHz
Figure 3.24: Results of Dhrystone and Whetstone benchmark AMD Athlon XP 1700+ overclocked to 3,107.05 MHz
Figure 3.25: Integer and floating-point results of testing AMD Athlon XP 1700+ overclocked to 3,107.05 MHz
Figure 3.26: RAM results of testing AMD Athlon XP 1700+ overclocked to 3,107.05 MHz
The performance of the AMD Athlon XP 1700+ processor overclocked to 3,107.05 MHz and cooled using liquid nitrogen can be evaluated according to the test results shown by SiSoftware Sandra.
Results for Athlon XP 1700+ (3,107.05 MHz)
Results for Pentium 4 2.8 GHz
Dhrystone ALU (MIPS)
Whetstone FPU (MFLOPS)
2,408 5,250 (SSE2)
Integer aEMMX/aSSE (it/sec)
RAM integer buffered aEMMX/ aSSE bandwidth (MB/sec)
RAM floating-point buffered aEMMX/aSSE bandwidth (MB/sec)
As a result of extreme overclocking of the AMD Athlon XP 1700+ processor, its clock frequency (1,467 MHz) was increased 112% to 3,107 MHz. This corresponds to a rating of 4000+.
To conclude, it is necessary to
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