PCI Bus Transactions

5.2.4.3Write-Through

When the 21555 is able to obtain access to the target bus and start transferring write data to the target before the transaction has been terminated on the initiator bus, it automatically enters flow-through mode. In flow-through mode, the 21555 can sustain long write bursts as long as a queue-empty condition is detected in posted write buffers or until an aligned disconnect boundary is reached. A queue-empty condition exists when the number of Dwords left in the posted write buffer is less than an unaligned cache line amount. When the queue-empty condition is detected, the 21555 master terminates the transaction on the target bus. When an aligned disconnect boundary is reached, the 21555 returns a target disconnect on the initiator bus. Flow-through mode behavior is used for both memory write and MWI commands.

5.2.4.4Memory Write Disconnect Mode

The 21555 implements a Memory Write Disconnect Mode bit in device specific configuration space. When enabled, the 21555 disconnects memory writes on aligned cache line boundaries, using the cache line size corresponding to the target bus

5.2.4.5Posted Write Queue Tuning

The 21555 implements a posted write queue management control bit for each posted write queue in the Chip Control 1 configuration register. This bit specifies at what threshold the 21555 returns a target retry instead of accepting write data. Setting this bit can minimize fragmentation of posted write transactions and can prevent bursts from being broken into sub-cache line bursts. The tuning options are as follows:

•Target retry is returned when less then a cache line is free.

For a posted write starting on an odd Dword address, the threshold is CLS-1 Dword entries free.

•Target retry is returned when less then half a cache line is free, for CLS = 8, 16, or 32 Dwords.

When the posted write queue is designated as full, the 21555 returns a target retry to the initiator and does not post any write data. The 21555 uses the Cache Line Size corresponding to the target bus for the target retry threshold.

21555 Non-Transparent PCI-to-PCI Bridge User Manual

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Intel 21555 user manual Write-Through
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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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