AMD 27493, 10, 27488 manual Front-Side Bus Sense Truth Table, FLUSH# Pin, IGNNE# Pin, INIT# Pin

Preliminary Information

26237C —May 2003 AMD Athlon™ XP Processor Model 10 Data Sheet

signals High above 2.5 V. Do not expose these pins to a differential voltage greater than 1.60 V, relative to the processor core voltage.

Refer to “VCC_2.5V Generation Circuit” found in the section, “Motherboard Required Circuits,” of the AMD Athlon™ Processor Motherboard Design Guide, order# 24363 for the required supporting circuitry.

See “Frequency Identification (FID[3:0])” on page 25 for the

DC characteristics for FID[3:0].

FSB_Sense[1:0] Pins FSB_Sense[1:0] pins are either open circuit (logic level of 1) or are pulled to ground (logic level of 0) on the processor package with a 1 kΩ resistor. In conjunction with a circuit on the motherboard, these pins may be used to automatically detect the front-side bus (FSB) setting of this processor. Proper detection of the FSB setting requires the implementation of a pull-up resistor on the motherboard. Refer to the AMD Athlon™ Processor-Based Motherboard Design Guide, order# 24363 and the technical note FSB_Sense Auto Detection Circuitry for Desktop Processors, order# TN26673 for more information.

Table 26 is the truth table to determine the FSB of desktop processors.

Table 26. Front-Side Bus Sense Truth Table

FSB_Sense[1]	FSB_Sense[0]	Bus Frequency
1	0	RESERVED
1	1	133 MHz
0	1	166 MHz
0	0	200 MHz

	The FSB_Sense[1:0] pins are 3.3-V tolerant.
FLUSH# Pin	FLUSH# must be tied to VCC_CORE with a pullup resistor. If a
	debug connector is implemented, FLUSH# is routed to the
	debug connector.
IGNNE# Pin	IGNNE# is an input from the system that tells the processor to
	ignore numeric errors.
INIT# Pin	INIT# is an input from the system that resets the integer
	registers without affecting the floating-point registers or the
	internal caches. Execution starts at 0_FFFF_FFF0h.

Chapter 11 Pin Descriptions 75