PCI Bus Transactions

5.3Delayed Write Transactions

The 21555 uses delayed transactions when forwarding I/O writes from one PCI interface to the other. Delayed transactions are also used for CSR or configuration register writes that cause the 21555 to initiate a transaction on the opposite interface, such as:

•CSR or configuration register write access that causes the 21555 to initiate a configuration write transaction.

•CSR write access that causes the 21555 to initiate an I/O write transaction.

When an I/O write intended for the opposite PCI bus is first initiated, the 21555 returns a target retry. When the delayed transaction queue is not full and if a transaction having the same address and bus command does not already exist in the delayed transaction queue, the 21555 queues the transaction information:

•Including address.

•Bus command.

•Write data.

•Byte enables.

Note: The byte enables are not checked when the 21555 decides whether to queue a delayed write transaction.

•When the transaction queued is a result of an I/O Configuration Data register write, the 21555 queues the appropriate data based on the type of access desired, the address and data contained in the corresponding registers, and the byte enables used for the register access. This phase of the delayed transaction is called a delayed write request (DWR).

•The 21555 requests the target bus and initiates the delayed write transaction as soon as the 21555 ordering rules allow. (See Section 5.7). The 21555 always performs a single 32-bit data phase when initiating a delayed write transaction. The 21555 completes the transaction on the target bus and adds the completion status to the queue. Completion status contains the type of termination (TRDY#, target abort, master abort) and whether PERR# assertion was detected. This phase of the delayed transaction is called the delayed write completion (DWC).

When the 21555 receives 224 consecutive target retries from the target, it discards the delayed write request and conditionally asserts SERR# on the initiator bus. See Chapter 12. This retry counter may be disabled by setting the retry counter disable bit in the Chip Control 0 Configuration register. When the transaction is discarded before completion, the 21555 returns a target abort to the initiator.

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21555 specifications

The Intel 21555 is a prominent microprocessor developed by Intel, designed to cater to a variety of computing needs. This processor marks a significant step forward in Intel's lineup and underscores the company's commitment to advancing technology in personal computing, enterprise solutions, and beyond.

One of the standout features of the Intel 21555 is its advanced architecture. It utilizes a multi-core design, enabling improved performance through parallel processing. This architecture allows multiple applications to run seamlessly without a decline in speed. The cores are built on a cutting-edge manufacturing process that enhances energy efficiency while maintaining high clock speeds.

The Intel 21555 supports a wide range of technologies, including Intel Turbo Boost, which enables dynamic adjustments to the processor’s performance based on workload demands. This feature allows the processor to accelerate its speed during intensive tasks, providing users with a responsive experience when it matters the most.

Another key characteristic of the Intel 21555 is its support for integrated graphics. With Intel UHD Graphics technology, users can enjoy enhanced visuals for everyday tasks such as video playback, web browsing, and light gaming. This eliminates the need for a separate graphics card for many users, particularly in home office or light gaming scenarios.

Security is a significant focus in the design of the Intel 21555. It includes built-in hardware-based security features like Intel Trusted Execution Technology and Secure Boot. These features help protect against various types of threats, ensuring that user data remains secure from malicious attacks.

The Intel 21555 is also optimized for use with Intel's platform technologies, including Intel Optane memory and Intel Rapid Storage Technology. These technologies work together to deliver faster boot times and improved system responsiveness, making computing more efficient for users.

Furthermore, the Intel 21555 is designed to support virtualization technologies, allowing multiple operating systems to run concurrently without compromising performance. This is particularly useful for developers and businesses that rely on virtualization for testing and development environments.

In summary, the Intel 21555 is a powerful and versatile processor that reflects Intel's ongoing innovation in the computing space. With its multi-core architecture, enhanced graphics capabilities, strong security features, and advanced technologies, it stands out as an excellent choice for a wide range of applications, serving both casual users and professionals alike.
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