AMD 8 manual Interface Signals, Overview, Signaling Technology, Preliminary Information, Chapter

Preliminary Information

25175H —March 2003 AMD Athlon™ XP Processor Model 8 Data Sheet

2 Interface Signals

This section describes the interface signals utilized by the

AMD Athlon™ XP processor model 8.

2.1Overview

The AMD Athlon™ system bus architecture is designed to deliver excellent data movement bandwidth for next- generation x86 platforms as well as the high-performance required by enterprise-class application software. The system bus architecture consists of three high-speed channels (a unidirectional processor request channel, a unidirectional probe channel, and a 64-bit bidirectional data channel), source-synchronous clocking, and a packet-based protocol. In addition, the system bus supports several control, clock, and legacy signals. The interface signals use an impedance controlled push-pull, low-voltage, swing-signaling technology contained within the Socket A socket.

For more information, see “AMD Athlon™ System Bus Signals” on page 6, Chapter 11, “Pin Descriptions” on page 55, and the AMD Athlon™ System Bus Specification, order# 21902.

2.2Signaling Technology

The AMD Athlon system bus uses a low-voltage, swing-signaling technology, that has been enhanced to provide larger noise margins, reduced ringing, and variable voltage levels. The signals are push-pull and impedance compensated. The signal inputs use differential receivers that require a reference voltage (VREF). The reference signal is used by the receivers to determine if a signal is asserted or deasserted by the source. Termination resistors are not needed because the driver is impedance-matched to the motherboard and a high impedance reflection is used at the receiver to bring the signal past the input threshold.

For more information about pins and signals, see Chapter 11, “Pin Descriptions” on page 55.

Chapter 2 Interface Signals 5