Initialization Requirements

The remainder of the 21555 configuration proceeds as described in Section 6.3.1.

6.3.3Without Local Processor

Initialization of the 21555 is possible without a local processor, or without local processor intervention. Serial preload is still performed as described in (Section 16.10). However, the serial load must clear the Primary Lockout Reset Value bit to allow access of configuration registers from the primary interface. The serial preload must successfully preconfigure the forwarding BAR setup registers, as well as overwrite primary read-only registers as necessary.

Upon completion of the serial preload, all configuration registers are accessible for PCI configuration from the host on the primary bus. The host is then also responsible for configuring the secondary interface and device-specific configuration registers.

6.3.4Without Local Processor and Serial Preload

When neither the SROM nor a local processor is present, only the reset values of all the read-only registers are used, and all forwarding BARs are disabled and do not request space (since all these registers are set up from the secondary side only). The 21555 configuration registers are accessible, and the 21555 CSR registers can still be mapped into memory or I/O space. However, the Table 107, “Primary Expansion ROM BAR” on page 175 is disabled. A parallel ROM (PROM) can still be accessed through the CSR mechanism. Configuration and I/O transactions can be forwarded through the indirect CSR mechanism; the I20 message unit, doorbell registers, and scratchpad registers are all accessible. The 21555 configuration registers that are accessible only from the secondary interface can be written using the downstream indirect configuration mechanism.

6.3.5Without Host Processor

Initialization of the 21555 can be performed without a host processor. In this case, the local processor must perform the initialization of the primary configuration registers from the secondary interface.

6.4Power Management Support

The 21555 implements the PCI Power Management interface on behalf of the subsystem. The 21555 Power Management interface is designed to be flexible to meet the varying needs of different types of subsystem functions. To fully understand the PCI Power Management interface, please refer to the PCI Power Management Specification, Rev 1.0. Some functions may need minimal power management support: the D0 and D3hot power states, without PME# support. Other functions may need all four power states and PME# support. Power management setup is done by SROM preload.

The SROM preload allows the following power management parameters to be defined:

•Power Management revision number.

•D1 power management state support.

•D2 power management state support.

•PME# support.

•Power Management Data register support.

•Device Specific Initialization status bit.

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

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Intel 21555 user manual Power Management Support, Without Local Processor and Serial Preload, Without Host Processor
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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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