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How Many Transistor in a CPU? Will it still work if one is broken?

The CPU is the core component of the computer, which is responsible for executing various instructions and operations. The performance and stability of the CPU directly affect the operating efficiency and reliability of the computer. So, how many transistors are there in the CPU? If one of the transistors is broken, will the CPU stop working?

How many transistors are in a CPU?

A transistor is a semiconductor device that can be used to amplify signals, switch circuits, store data, etc. The size and number of transistors determine the integration and performance of the CPU. With the advancement of manufacturing technology, the size of transistors is getting smaller and smaller, and the number is increasing. The most advanced CPU manufacturing process has reached the 3 nanometer (nm) level. 2nm chips are expected to be launched in 2025.

CPU Manufacturing Process Timeline

CPU Manufacturing Process Timeline(Data Sources: TSMC)

Depending on the CPU model and architecture, the number of transistors in the CPU is also different. Generally speaking, desktop and server-level CPUs have more transistors than mobile devices and embedded systems. For example, the M4 chip just released by Apple in May 2024 has 28 billion transistors, while the M2 Ultra chip released in June 2023 has 134 billion transistors. Among them, Apple's M4 chip is mainly used in mobile devices such as tablets and notebooks, while the M2 Ultra chip is used for desktop devices (Mac desktops).

M2 Ultra Chip

M2 Ultra Chip

What happens if a transistor in a CPU fails?

If a transistor in the CPU is broken, will it affect the normal operation of the CPU? This depends on where the broken transistor is and how it broke.

The broken transistor is in an unimportant position. Not all transistors in the CPU are necessary. Some transistors are only used for testing, debugging, manufacturing or verification, and are not needed in actual use. If these transistors are broken, it will not affect the function of the CPU at all, and it can even save some power consumption.

Transistors in CPU

Enlarged view of transistors in CPU

Broken transistors have redundant designs or repair mechanisms. Some important or sensitive circuits in the CPU, such as storage cells, arithmetic logic units, reference currents, etc., may have some redundant designs or repair mechanisms to cope with possible damage or aging. For example, there may be some spare cells or bits in the storage cells to replace the broken cells.

Broken transistors affect some functions or performance. If the broken transistor is in an important but non-fatal position, it may cause some CPU functions to be lost or performance to decline. For example, if a core or a memory channel is broken, the CPU will reduce the number of cores or memory bandwidth; if the core graphics card is broken, the CPU will lose graphics processing capabilities. In this case, the CPU can still work, but not as well as a good CPU.

Transistors in different locations

Transistors in different locations in the CPU

A broken transistor causes the CPU to completely stop working. If the broken transistor is in a very critical position, the CPU may not work at all. If the power management circuit, clock generation circuit, instruction decoding circuit, etc. are broken, the CPU cannot start or execute any instructions. In this case, the CPU is equivalent to a piece of scrap metal.

Another possibility is that the CPU itself has a broken transistor. In order to reduce costs, Intel will downgrade some defective Core i9 processors to Core i7 or even i5 by shielding the broken core or cache. This can fully utilize production capacity and expand the market, and consumers can also buy seemingly good chips at a cheaper price.

Intel i5, i7 and i9 CPU

Intel i5, i7 and i9 CPU

Do more CPU transistors mean more performance?

Hundreds of millions of transistors in a CPU

In general, more transistors on a CPU can potentially mean better performance, but it's not that simple or direct. The relationship between the number of transistors a CPU has and its overall performance is complex and multifaceted. Here's why:

  • Computational Power: Each transistor on a CPU acts as a switch involved in the processes of storing data or performing calculations - the basic duties of a processor. Therefore, theoretically, having more transistors would allow a CPU to perform more of these basic operations at one time, thereby increasing its computational power.

  • Multithreading and Multicore Design: As more transistors are available, CPUs can be designed with multiple cores. A core is essentially a unit that can perform tasks independently of other cores in the CPU. Modern software often utilises multithreading, which allows a task to be split into multiple smaller tasks and processed independently, then put back together. This technical capability requires a multicore design that can only be made possible by having more transistors.

  • Advanced Features: Additional transistors allow for the introduction of advanced features that can improve efficiency and speed. For example, a larger cache memory (which stores data for short-term immediate access) can be provided, which reduces the delay in retrieving information and increases computing speed.

However, the above points are all under the assumption that we are able to utilize these additional transistors effectively - which isn't always the case. Here are some factors that can complicate this scenario:

  • Thermal Limitations: Transistors generate heat when they operate. Cramming more and more transistors into a chip without the necessary corresponding improvements in heat management can lead to overheating issues, which can negatively impact performance and potentially damage the CPU.

  • Software Limitations: Software must be designed with multicore processing in mind to take full advantage of multicore CPUs, which is not always the case. For programs not designed in this way, additional cores will not result in better performance.

  • Diminishing Returns: Following Moore's law, which states that the number of transistors in a chip is expected to double approximately every two years, performance increase has begun to stagnate somewhat in recent years despite the continuous increase in transistor count, pointing towards diminishing returns in the relationship between transistor count and CPU performance.

So, while it's tempting to equate a higher transistor count with higher performance, a number of other factors can influence the final outcome. CPU design is a balancing act - designers must consider a wide range of issues including but not limited to transistor count, power usage, heat generation, task type and software optimization in order to produce a well-performing, efficient processor.

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1. What are transistors in CPU architecture?

Transistors are a fundamental component of CPUs (Central Processing Units). They act like switches that can be turned on and off to represent different states of binary code, 1 and 0 respectively. The transistors in a CPU form what are called logic gates, which perform various logical operations on binary data, from basic ones like AND, OR, NOT, to more complex functions that calculating operations entail.

2. How do transistors in a CPU work?

Transistors in a CPU function as electronic switches. They can be turned 'on' (allowing electric current to flow through) or 'off' (not allowing current to flow), thereby representing binary values of 1 (on state) and 0 (off state), which all computer data and instructions are based on. Through intricate combinations of these on and off states, CPUs can perform complex processes and calculations.

3. What is the significance of transistor density in a CPU?

Transistor density refers to the number of transistors that can fit into a given area on a chip. A higher transistor density generally means that more processing power and functionality can be packed into a single chip of a given size.

When transistor density increases, it usually comes with improvements to the CPU's computational speed, power efficiency, and potential capability set. This is due to the fact that smaller transistors can switch on and off faster (thus improving speed), consume less energy (increasing power efficiency), and more transistors can be placed on the same sized chip (increasing the compute resources available for given tasks).

4. How many transistors does Apple's M2 Ultra chip have?

Apple's M2 Ultra chip, released in June 2023, has 134 billion transistors.

5. What was the first CPU in the world?

The first CPU in the world was the Intel 4004, introduced in 1971. It was a 4-bit central processing unit and was designed for use in a calculator. It had 2300 transistors and was clocked at a maximum of 740 kHz. It was the first commercially available microprocessor by Intel and began the era of modern computing.

6. How many transistors in a CPU and GPU 2024?

As of 2024, the CPU with the most transistors is Apple's M2 Ultra chip released in June 2023, which has 134 billion transistors, and the GPU with the most transistors is Nvidia's Blackwell-based B100 accelerator, which is built on TSMC's custom 4NP process node and has a total of 208 billion transistors.

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