Special Applications, Programming Notes, Addressing

Introduction

2.3Special Applications

2.3.1Primary Bus VGA Support

The 21555 provides hardware support that allows configuration of itself as a Video Graphics Adapter (VGA) device. The primary class code should be preloaded through the serial ROM (SROM) or loaded by the local processor with the value for a VGA device (Base Class 03h, Sub-Class 00h, Programming Interface 00h). This allows the 21555 to present itself to the host as a VGA device.

The VGA Mode field in the Chip 0 Control register (see page 156) should be set to 01b to enable decoding of VGA transactions on the primary bus for forwarding to the secondary bus. These bits can be set through SROM preload, or either from a primary or secondary bus configuration write. Table 4 gives addresses that are decoded.

Table 4. Decoded and Not Decoded Addresses

	Memory addresses	[000BFFFFh : 000A0000h]

	I/O addresses:	AD[9:0]3BBh:3B0h
	I/O addresses:	3DFh:3C0h
		3DFh:3C0h

	Bits not decoded.	AD[31:16]000h
	Bits not decoded.	(No address translation is performed on these addresses.)
		(No address translation is performed on these addresses.)

The 21555 cannot be enabled as a snooping agent on the primary bus. This is because the 21555 cannot guarantee that it can buffer and forward all palette writes, since the 21555 has finite buffer space and no backoff mechanism when snooping. The 21555 should not be configured to appear as a VGA device in those applications where it may try to configure the 21555 as a snooping agent.

The parallel ROM can be used to store VGA BIOS code, which is mapped through the Primary Expansion ROM BAR.

2.3.2Secondary Bus VGA Support

The 21555 can be enabled to decode VGA transactions on the secondary bus for forwarding to the primary bus. This is done by setting the VGA Enable field in the Chip Control 0 register to 10b. The addresses that are decoded are the same as for the primary VGA decode, and again the addresses are not translated.

Upstream forwarding of VGA transactions can be useful for applications that want to allow access to a primary bus VGA device frame buffer by local processors in intelligent I/O or embedded subsystems.

Note: VGA decoding must not be enabled for both the primary and secondary interface. The value 11b is illegal for the VGA Enable field and can yield unpredictable results.

2.4Programming Notes

2.4.1Addressing

The non-transparent addressing model that the 21555 uses can cause problems if not programmed properly. Programming errors include:

20	21555 Non-Transparent PCI-to-PCI Bridge User Manual

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.

Intel 21555 Special Applications, Programming Notes, Primary Bus VGA Support, Addressing

Models: 21555