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HP dc7900 manual PCI Express Bus Operation, Software/Driver Layer, Transaction Protocol Layer

Models: dc7900

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System Support

The PCI bus supports a bus master/target arbitration scheme. A bus master is a device that has been granted control of the bus for the purpose of initiating a transaction. A target is a device that is the recipient of a transaction. The Request (REQ), Grant (GNT), and FRAME signals are used by PCI bus masters for gaining access to the PCI bus. When a PCI device needs access to the PCI bus (and does not already own it), the PCI device asserts its REQn signal to the PCI bus arbiter (a function of the system controller component). If the bus is available, the arbiter asserts the GNTn signal to the requesting device, which then asserts FRAME and conducts the address phase of the transaction with a target. If the PCI device already owns the bus, a request is not needed and the device can simply assert FRAME and conduct the transaction. Table 4-2 shows the grant and request signals assignments for the devices on the PCI bus.

Table 4-2.

PCI Bus Mastering Devices

Device

REQ/GNT Line

Note

 

 

 

PCI Connector Slot 1

REQ0/GNT0

[1]

 

 

 

PCI Connector Slot 2

REQ1/GNT1

[1]

 

 

 

PCI Connector Slot 3

REQ2/GNT2

[2]

 

 

 

NOTE:

[1]SFF and CMT form factors only.

[2]CMT form factor only

PCI bus arbitration is based on a round-robin scheme that complies with the fairness algorithm specified by the PCI specification. The bus parking policy allows for the current PCI bus owner (excepting the PCI/ISA bridge) to maintain ownership of the bus as long as no request is asserted by another agent. Note that most CPU-to-DRAM accesses can occur concurrently with PCI traffic, therefore reducing the need for the Host/PCI bridge to compete for PCI bus ownership.

4.2.2 PCI Express Bus Operation

The PCI Express (PCIe) v1.1 bus is a high-performace extension of the legacy PCI bus specification. The PCI Express bus uses the following layers:

■Software/driver layer

■Transaction protocol layer

■Link layer

■Physical layer

Software/Driver Layer

The PCI Express bus maintains software compatibility with PCI 2.3 and earlier versions so that there is no impact on existing operating systems and drivers. During system intialization, the PCI Express bus uses the same methods of device discovery and resource allocation that legacy PCI-based operating systems and drivers are designed to use.

Transaction Protocol Layer

The transaction protocol layer processes read and write requests from the software/driver layer and generates request packets for the link layer. Each packet includes an identifier allowing any required responcse packets to be directed to the originator.

 

Technical Reference Guide

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HP dc7900 manual PCI Express Bus Operation, Software/Driver Layer, Transaction Protocol Layer, PCI Bus Mastering Devices
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dc7900 specifications

The HP dc7900 is a well-regarded desktop solution that serves as a testament to HP's commitment to performance, reliability, and user accessibility. Introduced as part of HP’s Compaq line and designed primarily for business professionals, the dc7900 combines powerful processing capabilities with a compact form factor that suits various office environments.

One of the standout features of the HP dc7900 is its robust configuration options. It typically comes equipped with Intel's Core 2 Duo or Quad processors, giving users the ability to handle demanding applications seamlessly. The inclusion of Intel's technologies, such as Intel vPro, enhances remote management and IT control, making it an ideal choice for businesses looking to streamline their operations.

The dc7900 is designed with flexibility in mind. It offers multiple form factors, including mini-tower, small form factor, and ultra-slim desktop configurations. This variety enables organizations to choose a model that best fits their workspace requirements, maximizing both efficiency and aesthetics. The small footprint models are particularly beneficial in space-constrained environments, while the mini-tower version provides expandability for future upgrades.

In terms of graphics capabilities, the HP dc7900 typically features integrated Intel graphics, with options to install discrete graphics cards for users who require enhanced visual performance. This makes the dc7900 suitable for tasks ranging from standard office applications to more graphics-intensive responsibilities.

Connectivity is another key characteristic of the HP dc7900. It is equipped with a variety of ports, including USB 2.0 and audio jacks, allowing users to connect peripherals easily. Additionally, the dc7900 supports legacy connections, making it easier for businesses with older equipment to integrate new systems without hassle.

Durability and reliability are hallmarks of the HP dc7900. Built with high-quality materials and subjected to rigorous testing, this desktop is designed to withstand the demands of a bustling office environment. Furthermore, HP's comprehensive warranty and support options assure businesses of the reliability of their investment.

The HP dc7900 is not just a powerful desktop; it’s a versatile and dependable solution for modern businesses. With its combination of performance, expandability, and solid build quality, the dc7900 remains a relevant choice for those looking to enhance their productivity and efficiency in the workplace.