CPU speed or clock speed is one factor that determines computer performance. The higher the CPU speed, the faster the computer can perform calculations and run programs. In the 1970s to 2000s, CPU speeds increased drastically from a few megahertz (MHz) to several gigahertz (GHz).
However, in the last decade, the increase in CPU speed seems to slow down and stagnate between 3-5 GHz. Why is this happening? What hinders the development of CPU speed? Is there a maximum limit for CPU speed?
Bardimin will answer these questions by explaining some factors that affect CPU speed and the challenges faced by engineers and scientists in improving CPU speed.
Factors Affecting CPU Speed
CPU speed can be measured in two ways, namely clock rate and instructions per cycle (IPC). The clock rate is the number of cycles a CPU can perform in one second. The unit used to measure clock rate is the hertz (Hz), which means one cycle per second. Instructions per cycle (IPC) are the number of instructions that the CPU can execute in a cycle.
Instructions are basic commands that can be understood by the CPU, such as addition, subtraction, multiplication, division, and so on. The number of instructions that the CPU can execute in a single cycle depends on the design and architecture of the CPU. CPU speed can be calculated by multiplying the clock rate and IPC. For example, if the CPU has a clock rate of 4 GHz and IPC 2, then the CPU speed is 8 billion instructions per second.
Factors that affect clock rate and IPC include:
1. Transistor size
A transistor is an electronic component that functions as a switch to control the flow of electric current. Transistors can change form on (conducting current) to off (stopping current), or vice versa, quickly. Transistors are used to form logic gates, which are circuits that can perform logical operations, such as AND, OR, NOT, and so on.
Logic gates are used to form circuits, which are circuits that can perform certain functions, such as addition, subtraction, multiplier, and so on. Circuits are used to form units, parts of the CPU that perform certain tasks, such as arithmetic, logic, control, memory, and so on. The units are used to form the CPU. So, transistors are the basic elements of the CPU.
The smaller the transistor size, the more transistors can fit into the CPU. The more transistors loaded into a CPU, the more logic gates, circuits, and units can be created in the CPU. The more logic gates, circuits, and units created in the CPU, the higher the IPC the CPU can reach.
In addition, the smaller the transistor size, the shorter the distance that the electric current in the CPU must travel. The shorter the distance that the electric current in the CPU must travel, the faster the CPU can change from one state to another. The faster the CPU can change from one state to another, the higher the clock rate the CPU can achieve. So, transistor size positively affects CPU speed.
2. Voltage and power
Voltage is the difference in electric potential between two points. Power is the rate of electrical energy consumed or emitted by a device. Voltage and power are closely related to CPU speed. The higher the voltage applied to the CPU, the stronger the electric current flowing in the CPU.
The stronger the electric current flowing in the CPU, the faster the CPU can change from one state to another. The faster the CPU can change from one state to another, the higher the clock rate the CPU can achieve. So, voltage positively affects CPU speed.
However, voltage also negatively affects CPU speed. The higher the voltage applied to the CPU, the greater the power consumed by the CPU. The greater the power consumed by the CPU, the greater the heat generated by the CPU.
The greater the heat generated by the CPU, the higher the temperature that the CPU must handle. The higher the temperature that the CPU has to handle, the greater the risk of damage or failure that can occur to the CPU. So, voltage negatively affects CPU speed.
3. Cooling
Cooling is the process of reducing the temperature of an object or system. Cooling is closely related to CPU speed. The better the cooling provided to the CPU, the lower the temperature that the CPU must handle.
The lower the temperature that the CPU has to handle, the less risk of damage or failure that can occur to the CPU. The less risk of damage or failure that can occur to the CPU, the higher the clock rate that the CPU can achieve. So, cooling has a positive effect on CPU speed.
However, cooling also negatively affects CPU speed. The better the cooling provided to the CPU, the greater the cost to build and run the cooling system.
The greater the cost of building and running a cooling system, the greater the burden that CPU manufacturers and consumers must bear. So, cooling negatively affects CPU speed.
Challenges in Increasing CPU Speed
From the factors affecting CPU speed, it can be seen that there are several challenges faced by engineers and scientists in increasing CPU speed. These challenges include:
1. Physical limits
Physical limits are limitations determined by the laws of physics. The physical limits relating to CPU speed are transistor size, voltage, and heat. The size of the transistor cannot be reduced continuously without causing problems. One problem that can arise is quantum tunneling, which is a phenomenon in which electrons can cross transistors without being hindered by potential obstacles.
Quantum tunnelling can cause transistors to become unstable and unable to function properly. The smallest transistor size that can be made today is about 5 nanometres (mm), and it is estimated that the size of the smallest transistor that can be made in the future is about 1 nm. So, transistor size has a physical limit that cannot be crossed.
The voltage also cannot be increased continuously without causing problems. One problem that can arise is overheating, which is a phenomenon where the CPU temperature becomes too high and exceeds the tolerance limit.
Overheating can cause the CPU to become damaged or shut down. The highest tolerable CPU temperature today is around 100°C, and it is estimated that the highest tolerable CPU temperature in the future will be around 200°C. So, voltage has a physical limit that cannot be crossed.
Heat also cannot be reduced continuously without causing problems. One problem that can arise is a cooling limit, which is a phenomenon where the cooling system cannot lower the CPU temperature lower than the ambient temperature.
Cooling limits can cause the CPU to not operate optimally. The lowest ambient temperature achievable today is about -273°C, and it is estimated that the lowest ambient temperature achievable in the future is around -273°C. So, heat has a physical limit that cannot be crossed.
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2. Economic limits
Economic limits are limitations determined by cost and demand. The economic limits related to CPU speed are production costs, operating costs, and consumption costs. Production cost is the amount of money that must be spent to make a CPU. Factors affect production costs, such as transistor size, voltage, and cooling.
The smaller the transistor size, the higher the voltage, and the better the cooling, the higher the production cost. Factors also influenced production costs, such as technology, raw materials, labor, and competition. The more advanced the technology, the scarcer the raw materials, the more expensive the labor, and the fiercer the competition, the higher the production cost.
Operating cost is the amount of money that must be spent to run a CPU. Factors affect operating costs, such as voltage, power, and cooling. The higher the voltage, the greater the power, and the better the cooling, the higher the operating cost. Factors also affected operating costs, such as efficiency, reliability, and safety. The lower the efficiency, the lower the reliability, and the lower the safety, the higher the operating costs.
Consumption cost is the amount of money that must be spent to buy a CPU. Factors influence the cost of consumption, such as production costs, operating costs, and demand. The higher the cost of production, the higher the cost of operation, and the lower the demand, the higher the cost of consumption. Factors also influenced the cost of consumption, such as quality, features, and brand. The lower the quality, the fewer features, and the less well-known the brand, the lower the consumption cost.
Of the three types of cost, it can be seen that there is a trade-off between CPU speed and cost. The higher the CPU speed, the higher the cost. The higher the cost to be incurred, the lower the profit that can be obtained. The lower the profit that can be obtained, the lower the motivation to increase CPU speed. So, costs have an economic limit that cannot be crossed.
Alternative Solutions to Increase CPU Speed
From the challenges faced by engineers and scientists in increasing CPU speed, it can be seen that several alternative solutions can be done to increase CPU speed. These alternative solutions include:
1. Multi-core
Multi-core is a CPU that has more than one core or core. The core is the part of the CPU that is responsible for performing calculations and running programs. By having more than one core, the CPU can perform more calculations and run more programs simultaneously.
This can increase CPU speed significantly. However, multi-core also has some disadvantages, such as difficulty in programming, increased power consumption, and decreased efficiency.
2. Parallel computing
Parallel computing is a computational method that divides a problem into several sub-problems that can be solved simultaneously by multiple CPUs or computers. By doing parallel computing, a problem can be solved faster and more efficiently.
However, parallel computing also has some disadvantages, such as complexity in design, communication, and synchronization, as well as limitations in scalability, portability, and security.
3. Quantum computing
Quantum computing is a computational method that uses the principles of quantum mechanics to perform calculations and execute programs. By using quantum computing, CPUs can perform calculations much faster and more powerful than conventional CPUs.
However, quantum computing also has some disadvantages, such as difficulties in manufacturing, operating, and maintaining, as well as limitations in compatibility, stability, and reliability.
Conclusion
CPU speed is one of the factors that determine computer performance. CPU speed can be measured in two ways, namely clock rate and instructions per cycle (IPC). CPU speed can be calculated by multiplying the clock rate and IPC. Factors that affect CPU speed include transistor size, voltage, power, and cooling.
The challenges faced by engineers and scientists in increasing CPU speed include physical limits and economic limits. Alternative solutions that can be done to increase CPU speed include multi-core, parallel computing, and quantum computing.
By knowing the factors, challenges, and solutions related to CPU speed, we can understand why CPU speed is not increasing as much as it used to, and what we can expect in the future.