The first contact with overclocking was in the era of Pentium, and the memory is still so clear. The rush at home 100 made me surpass 120. Perhaps this achievement is nothing in the eyes of many people now, but for me at the beginning, this is the first success in my overclocking career. At that time, overclocking did not have any cooling measures. When the chassis is opened, there is not even an electric fan on the CPU, only a huge heat sink, which is estimated to be 3-4 times that of the common heat sink now.

120 speed accompanied me to end my high school career, enter the university and leave home. I sold my first computer and began to fantasize about my new computer. 1at the end of 998, I heard for the first time that someone had surpassed Celeron 300 to 450, so I decided to choose Celeron. At the end of 1998, DIY concept was introduced to China, and overclocking began to attract people's attention. The serial number of the 333 I bought is SL2WM, which is the so-called best product. I easily added the external frequency to 100, and then added it to 1 13 half a year later. A few days later, the screen went black as soon as I turned it on, and I never turned it on again.

It was this summer vacation that I changed the CPU again. The dragon makes me very excited. Unfortunately, I didn't wait until AMD booked the warehouse. Near September, I spent 700 yuan to buy a DURON600. Much like last time, after I spent the summer safely at 8 octaves, I changed the octave to 10, hoping to usher in a beautiful autumn. As a result, the dragon burned to death.

The two CPUs left like this, and I finally gained experience in failure. Just talk about it and share it with everyone.

One: How soon do you need it? Many people overclock just to adapt to a popular DIY trend, but is DIY really overclocked? What do many people do with overclocked computers? Watch VCD, type and play simulator. That's it. Do you need to overclock? They think overclocking is to restore the real performance of CPU. In fact, overclocking is not to restore the real performance of CPU, but to make your own CPU run in the marginal state, which greatly improves the probability of CPU error. You let the CPU run on the edge just to watch VCD, type and play simulator? Is it worth it?

Two: temperature, have you ever cared about the temperature of your CPU? It's not just when you turn it on, simply press DEL to go in and have a look. The fan temperature can be controlled below 35 degrees. Have you ever paid attention to the temperature when the CPU is running at full capacity due to frequent disk reading, 3D graphics rendering or high-intensity 3D games? At high temperature, your CPU will migrate electronically, which will not necessarily burn out the CPU, but will shorten its service life.

Three: money. As we all know, this is the national condition of China. A good CPU may cost a month's salary, or more. So what are you thinking, are you still using your CPU to the limit? The old Celeron burned, but the boss changed. Now K7, hehe, forget it, even the trademark under the CPU burned. Will someone replace it?

I have no objection to overclocking. After all, overclocking is in line with the principle of doing more with less money, but the word moderate is so important. Don't let your CPU run on the brink of death.

Overclocking and system stability -CPU

As we all know, most CPUs in the market can overclock, among which Intel Celeron series has the best overclocking performance, but in fact, many friends' overclocking systems become unstable. Some friends' systems can run Win95 but crash easily, or they can run Win95 but can't run Need for Speed Ⅲ stably. Some DIYer blame it on the quality of CPU or memory chip. In my opinion, besides these two main factors, other aspects are equally important.

First, a stable motherboard.

As we all know, CPU, memory stick and all boards are plugged into the motherboard, so the stability of the motherboard has become the key to affect the stability of the whole system. A good motherboard must be very particular about material selection and workmanship, and the obvious one is the board slot used on the motherboard. In order to ensure product quality, some manufacturers often choose well-known brands recognized by the industry, such as Foxconn. Because of my work, I have tested almost all the slots on the market, and the cheapest one made in Zhejiang can withstand 30 plugs. The most expensive gold-plated imported goods, after hundreds of plugging and unplugging, also began to have poor contact. Although its material and technology are far superior to the former, when using computers, we should pay attention to reducing the number of plugging and unplugging cards and maintaining good contact with them. The filter capacitors on high-quality motherboards are almost all tantalum capacitors. Tantalum capacitor has small leakage current and good high frequency characteristics, while ordinary electrolytic capacitor has large leakage current and inductance. Although it is used for low-frequency filtering, the switching power supply of the computer works in frequency conversion mode, and its own ripple is relatively large. If the input and output terminals are not well filtered, the interference in the power grid will become more complex harmonics, coupled to the output DC voltage, so tantalum capacitors can filter out higher harmonics that are difficult to filter out by ordinary electrolytic capacitors. The flux on the surface of printed board used in high frequency circuit will make the high frequency characteristics of the circuit worse. After welding and debugging, the surface of printed board should be cleaned with special solvent. From the appearance, the high-quality motherboard has a smooth surface and full solder joints. Some motherboards have the design of automatically closing unused PCI, ISA and DIMM slots, which helps to reduce interference. There is a Spreadtrum switch in the chipset of the motherboard BIOS setting with this function.

Second, proper cooling equipment.

As we all know, there are three different forms of heat flow from the high temperature part to the low temperature part: 1. Conduction; 2. Convection; 3. Radiation.

The greater the temperature difference between the two ends of a metal rod with uniform mass, or the shorter the length of the rod, the greater the heat conduction, which is the basic theorem of heat conduction. The above relationship can be expressed by the following formula:

Q = λ a (t 1-t2)/l or q = λ a δ t/l.

Where q is the heat conducted per unit time, a is the cross-sectional area of the rod, l is the length of the rod, T 1 is the high-temperature end temperature of the rod, T2 is the low-temperature end temperature of the rod, and λ is the proportional constant or thermal conductivity.

Several common cooling devices:

1. radiator

The thermal conductivity of radiator is closely related to its material. Metal materials are generally materials with good thermal conductivity, but there are also differences. Pure copper has ideal thermal conductivity. The thermal conductivity of aluminum is 1/2 of copper, and that of steel is about 1/7 of copper.

Consider the method of increasing heat dissipation from the above formula: that is, the heat conductivity of radiator materials should be large, such as copper, aluminum and other materials; The area of the radiator should be large, and the increase of the heat dissipation area can increase the heat dissipation in proportion. The distance from the CPU or display chip to the radiator should be short, which means that the radiator should be as close as possible to the CPU or display chip. In order to make them fully contact, the surface of CPU or display chip should be evenly coated with heat conductive silica gel or heat dissipation paste.

Then install the radiator.

Radiators come in various shapes, some of which are made of plates and some of which are made of castings.

L is the thickness of radiator bottom plate, Af is the radiator surface area, A0 is the radiator bottom area, Ab is the radiator bottom area, Ta is the space temperature, and Ti is the temperature of the contact surface between radiator and heating parts. At this time, the heat emitted from the contact surface of the heating element through the radiator per unit time can be expressed by the following formula:

Where αi is the heat transfer coefficient inside the radiator, αm is the average heat transfer coefficient between the radiator and the air, and η is the radiator efficiency. It can be seen from the formula that the heat transfer coefficient αm is large and the η Af term is large, which can increase the heat dissipation, and the efficiency η of the heat sink is large, so materials with large thermal conductivity can be used. In order to increase Af, we should try to increase the height of radiator fins. Or make the fin thickness thinner and the number of fins increase, but blindly increasing the number of fins will make the convection worse, which will lead to a certain contradiction in the reduction of αm, so the number and size of fins are limited.

2. Fan

Fan is the most commonly used air-cooled equipment, and heat dissipation of electronic equipment is indispensable. Fans used to cool electronic equipment can be roughly divided into axial fans and centrifugal fans. The working principle of axial flow fan is to use the lift of fan blades to make air flow along the axial direction. Fan blades are generally directly connected to the motor, which is the most common one, with small volume and light weight. Centrifugal fans use centrifugal force, air flows along the radial direction of blades, which can get higher wind pressure and can be installed in occasions with large ventilation impedance.

3. Semiconductor refrigerator

The phenomenon that the electronic cooling element absorbs heat after being electrified is called the Peltier effect, which was discovered by the German scientist Peltier. When current is applied to the contact surface of dissimilar metals, the contact surface will generate or absorb heat, which will turn over due to the reversal of current direction, and the heat generated or absorbed per unit time is proportional to the current value. The structure and working principle of the semiconductor refrigerator are shown in Figure 2:

Two pieces of semiconductor materials, P-type and N-type, are welded between metal sheets A and B respectively. The main materials are bismuth telluride, antimony telluride and bismuth selenide. When the circuit is powered on, the metal sheet A absorbs heat and the metal sheet B emits heat. Put a radiator at the metal sheet B to dissipate heat.

4. Condensing radiator pipe

The condensing and radiating pipe is a cylindrical hollow container, and the wall of the pipe is filled with sintered metal, metal felt and other materials, which mainly makes the working liquid flow back from the upper condensing part to the lower evaporating part by using its large capillary force. When the evaporation part is heated, the working liquid is evaporated, and this vapor is quickly transferred to the condensation part, and quickly takes away heat, and is cooled in the condensation part to condense the gaseous working liquid into liquid and accumulate it. Because the working liquid in the evaporation part flows back due to the insufficient capillary force, the evaporation of industrial liquid (endothermic process) → the movement of steam (heat transfer) → condensation (exothermic process) → the working liquid flows back, and the heat conduction process of the container is automatically completed. This kind of condensation radiator has the advantages of good thermal conductivity, fast thermal response, simple structure, light weight, long service life, low failure rate, etc., and can be used without gravity. It also has the characteristics of thermal diode and thermal switch. In particular, the general solid conduction heat is inversely proportional to the length of the conduction path, while the condensation heat pipe has characteristics that other solid heat transfer does not have. When used in electronic equipment, one end can be connected with a plurality of heating elements, and the other end can be connected with a radiator and other heat dissipation devices of the casing, so that the heat dissipation effect is very ideal.

Third, the right chassis

The price of the chassis does not account for a large proportion in the price of the whole machine, but it cannot be ignored in the stability of the whole machine. Mainly reflected in two aspects:

1. Load capacity and anti-interference ability of power supply and chassis;

2. Heat dissipation design and airflow design inside the chassis.

Try to choose a larger chassis, which is not only more scalable, but also allows your PC to dissipate heat more effectively. Although the ultra-thin mini-tower cabinet looks small and exquisite, it is difficult to solve the heat dissipation problem in the overcrowded internal space.

fixed

1. Pay attention to the hazards of static electricity:

Pay attention to the static electricity carried by human body when assembling and repairing computers. The electrostatic charges in different parts of the human body are not equal, and it is generally believed that the potential on the wrist side is the highest. Therefore, when a human hand touches electronic equipment and devices, it will generate electrostatic discharge in an instant, which is generally pulsed, and its interference to electronic circuits generally depends on pulse amplitude, width and pulse energy. It is reported in related literature that the equivalent capacitance and equivalent resistance of human body are about 150pF and150Ω respectively when electrostatic discharge occurs. When discharging through human body resistance, the pulse width of discharge is 22.5ns, and the instantaneous power is very huge. Sometimes the charged voltage and energy are not very large, but because they work in a very short time, their instantaneous energy density will also cause interference and harm to circuits and devices. As we all know, CMOS circuits are most afraid of static electricity and are most easily damaged by static electricity. The insulation length of CMOS oxide film is generally around 106V/cm. For the oxide film with the thickness of 1μm, it can withstand 1KV. The thickness of the gate oxide film of CMOS devices determines that its withstand voltage limit is about 100 ~ 150V, which shows that people with thousands of volts of static electricity will come into contact with the circuit. At present, all devices are designed with internal protection circuits, such as extending a slender P layer on an N-type substrate to make the input terminal and UDD power supply have diode characteristics, and connecting the diffusion resistance of the P layer in series between the input terminal and the gate; The diffusible n layers are paired to form another diode. In this way, the input is protected between UDD and ground. However, this kind of diode is limited to the high-voltage protection of positive and negative polarity, and it can't be protected if there is a large energy electrostatic discharge at the input end, so the operator should wear an antistatic belt on his wrist and have good grounding performance. In your spare time, you can touch the tap water pipe with your hands to release static electricity.

2. Common sense of connecting wires:

Flat cable, commonly known as hard disk cable, is often used for signal transmission between components or circuit boards, such as IDE port and hard disk, IDE port and optical drive, floppy drive port and floppy drive. When each adjacent conductor of a flat cable is used, mutual coupling is easy to occur because the distributed capacitance between adjacent conductors is large. Generally, the distributed capacitance between lines of flat cable is 0.3 pf/10 cm ~ 3 pf/10 cm (test frequency is 1MHz), while the square wave pulse signal of microcomputer system ranges from several thousand to tens of MHz, and its burst frequency is as high as 33MHz in UltraDMA33 interface system. A square wave can be decomposed into the fundamental wave with the same frequency and its higher harmonics, and the higher harmonics of100th order should be considered. For such a high frequency, the impedance of these distributed capacitors is very low, so crosstalk interference is easy to occur. Therefore, the length of flat cable should generally not exceed 20cm. When used for a long distance, the signal transmission line should be isolated from the ground wire. There is a ground wire between the two signal wires, which plays a better shielding role. The data shows that the distributed capacitance between signal lines decreases from 0. 189pF to 0.023pF after increasing the ground isolation. I think this may be the reason why UltraDMA66 adds 40 ground wires. However, for the noise entering perpendicular to the cable direction, its suppression ability is still poor, so the cable should not be too long.

3. Installation of the motherboard:

Printed lines on the main board have high density and are placed close to each other. Because of the distributed capacitance between printed lines, crosstalk interference is caused. For manufacturers, to suppress this interference, first of all, when designing wiring, we should try to avoid long-distance parallel wiring between lines and widen the distance between lines as much as possible. Grounding signal lines can be set between some signal lines that are very sensitive to interference to prevent crosstalk between lines. In addition, if one side of the printed circuit board is grounded in a large plane, the crosstalk between printed wires on the other side can also be reduced, because the distributed capacitance between parallel wires becomes smaller when it approaches the ground plane. In addition, the higher the switching speed of the circuit, the higher the frequency component, and the easier it is to cause crosstalk under the same distributed capacitance. In order to reduce the crosstalk noise between printed wires, we should pay attention to reducing the impedance of printed wires to ground. For DIYer, we can adopt another flexible large plane grounding method, that is, when installing the computer motherboard, we use metal bolts to fix the motherboard on the chassis, instead of the plastic clips that some installers usually use. Motherboard manufacturers generally design the mounting holes as signal ground. Connecting the motherboard to the chassis made of galvanized iron plate can ground the chassis as a large plane, thus reducing the grounding impedance of the printed wires themselves and reducing the crosstalk noise between the printed wires.

4. System grounding:

The design and installation of microcomputer grounding system is an important problem of microcomputer anti-interference, which not only affects the anti-interference performance of microcomputer and external equipment, but also affects the safety of equipment and personal safety. Grounding system can generally be divided into lightning protection grounding, AC grounding, safety grounding, DC grounding and so on.

(1) lightning protection place: lightning rods are often erected in buildings to prevent lightning strikes, and conductors are used to introduce buried ground wires. This grounding device will generate a fairly high potential near the grounding area, because hundreds of kA of current will pass at the moment of lightning strike. In order to prevent lightning from disturbing other grounding systems or damaging equipment, it is generally required that such grounding resistance is less than10Ω and the distance from other grounding is more than 25m.

(2) AC grounding: AC grounding is the grounding system of commercial AC power supply. Take the commonly used single-phase urban power supply system as an example. At the power transformer, its neutral line is grounded. In this power supply system, the current flowing through the neutral line is mainly the loop current flowing through the load equipment, as well as the unbalanced current in normal state and the grounding current in abnormal state. Because the current flowing through the neutral wire changes greatly, the voltage drop formed by grounding current on the grounding wire also changes, and the potential between devices changes, forming interference. Therefore, it is hoped that the smaller the grounding resistance is, the better, and it should not exceed 4 Ω.

(3) Safety: Safety refers to the enclosure grounding system of various equipment. Because the bushing is grounded, it provides a low-impedance leakage channel for the high-frequency interference voltage induced on the bushing, which not only shields the equipment, but also prevents the accumulated charge on the bushing from causing the bushing voltage to rise or threatening the personnel who contact the bushing due to leakage. This grounding resistance is also required to be very small, not exceeding 4 Ω.

(4) DC ground: DC ground is the logical ground of electronic equipment composed of digital circuits. It connects the output terminal 0 of DC power supply to the ground network to obtain a stable zero potential of the system, and its resistance to ground should be less than 1ω. Because the logic "1" and logic "0" of TTL and CMOS circuits commonly used in microcomputer are only a few volts apart, the voltage drop fluctuation or noise of DC ground wire can easily lead to circuit misoperation, so the design and installation of DC ground wire is very important.

5. Heat dissipation of the whole machine:

The cooling methods of PC chassis can be divided into natural air cooling and forced air cooling:

Natural air cooling: We know that in air, when an object is heated, the surrounding air will flow from bottom to top due to natural convection. When several boards are placed side by side, the heat dissipation effect of vertical placement is definitely better than that of horizontal placement. For plates placed side by side and vertically, it is generally considered that the spacing between plates is wider or narrower. However, the experimental results show that the wider the spacing is, the lower the temperature will be. When the spacing is greater than 20mm, the temperature drop will slow down, and when it is greater than 30 mm, it will hardly change.

Forced air cooling: the simplest method of forced air cooling is to install a fan. The blowing force of the fan will cause strong airflow to quickly dissipate heat from the heating parts inside the machine.

The ATX chassis is reserved with an external fan, and the AT chassis can also be equipped with fans as required. The cooling effect of forced air cooling is much better than natural air cooling. No PC case will be airtight. Let's talk about the air leakage problem that should be paid attention to in forced air cooling. Air leakage mainly affects air volume. Usually, the installation types of fans are suction type, booster type and dual-purpose type.

√ Suction-out type: The fan is installed at the air outlet and is in suction state. At this time, the internal pressure of the chassis is lower than the external pressure, showing negative pressure, and external air is sucked from the slit hole. At this time, the air volume increases as it flows to the outlet.

√ In the supercharged type, the fan is installed at the entrance. At this time, the interior of the chassis is in a positive pressure state. Because the air leaks to both sides, the air volume gradually decreases and is the lowest at the exit.

√ The dual-purpose type is suction type and pressure type. The air pressure inside the module is divided into positive pressure part and negative pressure part, and the air flows out and in.

Generally speaking, air leakage will affect heat dissipation, but a little air leakage will sometimes increase the heat dissipation effect. In the case of forced air cooling, the ventilation design in the cabinet is very important, and the key is to have enough air inlet and outlet and reasonable air duct. If part of the air is directly sucked out of the cabinet without passing through the heating part, that is, the airflow flows out through the bypass, and the heat dissipation effect is obviously poor. For the overall cooling of the equipment, it is recommended to use an exhaust fan. After the exhaust fan is used, the airflow can be evenly distributed on each channel, and the heat of each heating component can be fully taken away. If the fan is used to blow into the chassis, due to the blocking effect of each plate, the airflow will be blocked and the heat dissipation effect will be poor. In addition, when installing the fan, it should be noted that there are fans with speed measurement in the market, and the power supply of the fan is directly provided by the motherboard. Although this method is simple to install, it can also display the fan speed in BIOS and monitoring software. However, if the power supply of the motherboard is insufficient or the fan power is too large, it will lead to the lack of power supply of the motherboard to other components, resulting in system instability. In severe cases, memory errors will occur frequently, which goes against our original intention. Therefore, it is recommended to use a fan directly connected to the main power supply, which will not only affect the stability of the system, but also reduce the price by about one third.

Some experiences:

1. If it is not necessary, try not to modify the board at the chip level, such as adding filter capacitors, series current limiting resistors or chokes. Because your modification may make your already unstable system more fragile. In the high frequency environment such as PC system, sometimes a bad solder joint will introduce uncontrollable interference. Especially in the amateur conditions without professional tools, you should think twice before you act.

2. Try not to increase or decrease the core voltage and I/O voltage of CPU. Because if your CPU really needs to increase the voltage to remain stable, then it is not a CPU suitable for overclocking. Even after increasing the voltage, it can keep stable operation and its service life will be greatly reduced. Don't do this unless you really want to upgrade your CPU. My IBM6x86MX200 overclocked to 83MHz×2.5. Because the system is unstable, the core voltage is slightly increased and a high-power fan is installed. Since then, the system has been running stably for a long time, even when the ambient temperature is 39℃, there is no fault. However, after 1 1 month, the CPU was permanently damaged. Fortunately, it is still under warranty, otherwise it will have to be upgraded.

3. On the issue of BIOS upgrade, if you don't need to add some functions because the BIOS doesn't support some devices, I suggest you don't upgrade the BIOS easily. Of course, if you have a programmer with as many FlashRom as I do, that's another matter.

Everyone knows that when playing overclocking, you should give the CPU a huge heat sink and a powerful fan. In fact, the heat dissipation of display chips is also very important. If the display chip is overheated, it will cause the screen to appear or crash. Some DIYer like overclocking graphics cards to improve display performance. At present, most of the graphics cards sold in the market are display chips made by 0.35μm process, including popular chips such as RivaTNT and VoodooBanshee. At higher frequencies, more attention should be paid to the heating of display chips. Most brand-name graphics cards are equipped with heat sinks and fans when they leave the factory, while some brand-name graphics cards only have heat sinks or no heat dissipation measures, which requires us to add them ourselves. Now there are ready-made heat sinks with glue on the market, just choose the right size and paste them.

Is overclocking related to software? -Central processing unit

You don't seem to believe that the system can also help overclocking? From my experience, this can be done. My computer was equipped in 1998. The CPU used is Celeron 333, the motherboard is Pan Ying BX2, the hard disk is 6.4G Quantum Fireball VII, and the graphics card is Riva128,32 HY memory. The configuration was not very bad at that time. After buying the computer, I started my own overclocking process.

We are not overclocking enthusiasts. What we can do is to realize it step by step according to the overclocking method introduced by some newspapers. First, we installed the system, which was windows98. Then, we enter COMS, adjust the system clock of CPU from the default 66MHz to 75MHz, and save the settings to exit and restart. At this time, we can see from the screen that the frequency of CPU is 375MHz(75×5). After the blue sky and white clouds, I entered windows98, and then I ran various programs and played Tomb Raider 3, Need for Speed 3 and other games. Everything was normal. Initial success has been achieved. Exit sindows98 and restart, then enter COMS to adjust the system clock of CPU to 83MHz, and restart the machine after saving. At this time, the frequency of CPU is displayed as 4 15(83×5). Then I successfully entered windows98, but after the program ran for a period of time, the mouse couldn't move, the computer crashed, and I repeated it several times. At that time, I felt that the memory capacity was too small to get on, so I took a 64-megabyte memory from my friend and tried again. The result is still not good, but when the CPU frequency is adjusted back to 75MHz, everything is normal and the operation is very stable. The final conclusion is that this CPU can only go up. I can't achieve my original intention when assigning planes, but I have been reluctant to let go.

With the release of windows2000, like many new fans, I installed a dual system for my machine, playing games with windows98 and surfing the Internet with windows2000 for a long time. One day, it suddenly occurred to me that windows2000 is famous for its stable operation, and its kernel is different from windows98. In this case, can you make your CPU super high? Try it when you think about it, then adjust the CPU frequency to 83MHz in COMS, reboot into windows2000, and then run some bigger software for testing. It's good that the system is relatively stable and there are no mistakes, and then running some games has not crashed. In order to verify whether windows2000 was installed, I rebooted into windows98, but it didn't take long for windows98 to crash. I tried several times. Finally, I confirmed that my CPU can run stably at the frequency of 83MHz in windows2000.

If a friend wants to overclock but can't overclock, and doesn't want to use any methods commonly used by overclocking enthusiasts, such as adjusting voltage and cooling CPU, and you happen to use windows95 and windows98, then you might as well try to overclock with windows2000, and there may be unexpected gains.

Comment: There are many factors that affect the success of overclocking. Not only the voltage, temperature and composition of CPU should be considered, but also many invisible factors that are easy to be ignored, including the frequency of peripheral devices and so on. These factors are often the key to the success of overclocking. In a word, overclocking can't be successful, but it doesn't necessarily mean that it can't be surpassed. We should look for other reasons, and sometimes we may even look for software factors.

The principle of overclocking -CPU

Today, overclocking is no secret, and overclocking has almost become a fashion. The definition of overclocking is simple: overclocking is to make an integrated circuit work beyond its specified clock speed. That's all.

The speed of the chip is determined by the clock and multiplier of the front-end bus. Now some advanced processors can run on 100.

Megahertz or higher front-end bus clock, while Celeron

The processor stays at 66.

Megahertz front-end bus clock.

A few years ago, you could overclock by choosing a more advanced multiplier. However, in order to counter the handling of "remarks" by the central authorities, this practice has now been completely abolished. Fake processors have begun to appear on the market regularly.