Backside Bus


The Backside Bus, also known as the backside system bus, is a computer bus used in CPUs for communication with the cache memory. It operates independently from the frontside bus, which connects the CPU with the main memory. This gives the CPU faster access to frequently used data stored in the cache.


The phonetic spelling of “Backside Bus” is: /ˈbækˌsaɪd bʌs/

Key Takeaways

Three Main Takeaways about Backside Bus

  1. The Backside Bus is primarily responsible for connecting the processor to the Level 2 cache, otherwise known as the secondary or external cache. Its main function is to transfer data between the processor and these high-speed storage areas.
  2. Backside Bus operates at a higher speed compared to the front-side bus. This speed disparity enables faster data transfer rates, resulting in higher overall system performance and smoother operations.
  3. The Backside Bus also influences the speed at which the CPU operates, as it determines how fast the CPU communicates with the cache memory. Therefore, a slow backside bus means slower CPU performance, and vice versa.


The technology term “Backside Bus” plays an important role in modern computing as it regulates the interaction between the processor and the Level 2 (L2) cache, which is also known as secondary or external cache. The backside bus connects the CPU with the cache memory and its speed is a critical factor in the smooth functioning of a computer system. This is because the L2 cache typically stores data that the CPU uses most often and connects directly to the processor. Therefore, a faster backside bus allows quicker data transfer between the CPU and the cache, thus improving the system’s overall speed and efficiency which results in improved performance of a computer system.


The Backside Bus is a specialized communication pathway employed in computers between the CPU and the cache. This technology was essentially applied to enhance the system’s overall performance by significantly reducing the time required for data exchanges. Essentially, the Backside Bus provides an express, direct line of communication between the CPU and Level 2 cache to speed up data transfers, which is crucial as the CPU is constantly fetching data from memory storage.The hardware technology designs of the been widely used to boost computer operational efficiency for multi-processor computer configurations which often involve multiple processors sharing common resources. This is particularly useful because simultaneous data transfer demands can lead to traffic congestion and slow system performance. A dedicated backside bus for each CPU to its respective cache can alleviate such issues by providing an unobstructed pathway for quick data exchanges. Thus, the primary function of the backside bus is to enable faster data transfer and provide a more efficient processing environment, which elevates overall system performance.


1. Computer Processors: The most common real-world example of a backside bus (BSB) can be found in computer processors. The term specifically refers to the data path that resides between the computer’s processor and the Level 2 cache usually inside the CPU. This pathway allows for rapid data transfer, thereby enhancing the device’s overall performance. For example, Intel’s Pentium Pro, Pentium II, and certain models of Pentium III and IV utilize the BSB technology.2. Apple Devices: Apple’s PowerPC G3 series employed distinct backside bus to connect the processor to the Level 2 cache. This separated pathway helped accelerate the communication speed between these components, thereby improving overall system performance.3. IBM Workstations: IBM’s workstations and servers that use the POWER3 and later chips use the backside bus to help improve cache access times for large databases and other applications that require high memory usage. This dedicated pipeline enhances overall performance and processing speed.

Frequently Asked Questions(FAQ)

**Q: What is Backside Bus?**A: Backside bus is a computer bus used in the operation of a computer system. It typically connects the microprocessor, or central processing unit (CPU), to the level 2 cache memory (L2 cache), providing a pathway for data.**Q: What is the main function of the Backside Bus?**A: The main function of the Backside Bus is to ensure a quick transfer of data between the computer’s processor and the L2 cache. This operation allows for swift fetching and storing of instructions and data required for computation.**Q: How does the Backside Bus enhance the performance of a computer system?**A: The Backside Bus enhances the speed at which the processor can access data from the cache memory by providing a dedicated connection. This leads to faster processing times, which overall enhances the performance of the computer system.**Q: How does Backside Bus differ from Front Side Bus?**A: The Front Side Bus (FSB) refers to the connection between the processor and the main memory or system memory, while the Backside Bus (BSB) is the connection between the processor and the L2 cache. The BSB typically operates at a higher speed than the FSB.**Q: How has the use of Backside Bus evolved over time?**A: With the progression of technology, many CPUs now integrate L2 cache directly onto the chip itself. Thus, they do not utilize a traditional independent backside bus. However, in systems that still use separate L2 cache, the concept of backside bus is absolutely relevant.**Q: How does Backside Bus speed impact the performance of a computer?**A: The speed of the Backside Bus directly correlates with the speed at which a processor can access data from the L2 cache. A higher bus speed implies faster data retrieval, which could lead to an overall increase in system performance, particularly in data-intensive tasks.

Related Technology Terms

  • Address Bus
  • Data Bus
  • Bus Speed
  • Chipset
  • Frontside Bus

Sources for More Information


About The Authors

The DevX Technology Glossary is reviewed by technology experts and writers from our community. Terms and definitions continue to go under updates to stay relevant and up-to-date. These experts help us maintain the almost 10,000+ technology terms on DevX. Our reviewers have a strong technical background in software development, engineering, and startup businesses. They are experts with real-world experience working in the tech industry and academia.

See our full expert review panel.

These experts include:


About Our Editorial Process

At DevX, we’re dedicated to tech entrepreneurship. Our team closely follows industry shifts, new products, AI breakthroughs, technology trends, and funding announcements. Articles undergo thorough editing to ensure accuracy and clarity, reflecting DevX’s style and supporting entrepreneurs in the tech sphere.

See our full editorial policy.

More Technology Terms

Technology Glossary

Table of Contents