Intel 460GX 2.6Interrupt Related Registers, 2.6.1SAC, Bits, XTPR, XTPR, XTPR, XTPR, XTPR, XTPR, Description, Bits Description

Register Descriptions

2.5.5.2PCI_WXB_PMC1: PCI Performance Monitor Configuration Register

Address Offset:	E8h – EBh	Size:	32bits
Default Value:	00000000h	Attribute:	Read/Write

This register controls the PCI performance monitors. There are two performance monitors for each PCI bus. This register defines the events to be monitored and when monitoring starts and stops. The selected event can be qualified by data transferred, and issuing agent.

Bits Description

31:0 See PCI_WXB_PMC0 definitions.

2.6Interrupt Related Registers

2.6.1SAC

2.6.1.1XTPRS: External Task Priority Registers

Bus CBN, Device Number:	00h	Function:	0
Address Offset:	C0-C7h	Size:	64 bits
Default Value:	80h	Attribute:	Read Only
Sticky:	No	Locked:	No

The XTPRS are used to support redirectable interrupts. These registers are made observable to software primarily for test and debug purposes. These registers will be updated by XTPR Update Special Cycle on the system bus. The second cycle of the XTPR Update Special Cycle’s address determines the value to load into the register. Ab[27:24]# is the 4 bit XTPR value. Ab[23:20]# determines which register to update. Since the high priority agent reserves the uppermost agent ID bit, only Ab[22:20]# are used. These 3 bits decode to one of the 8 registers. Ab[31] is the enable bit for the register.

All registers default to 1000_0000b, which is the disabled state.

Each register is defined as:

Bit 7 - enable (1=disable, 0=enable)

Bits 6:4 - reserved (0)

Bits 3:0 - value of XTPR

Bits	Description
63:56	XTPR 7
	These bits represent the external task priority for symmetric agent ID 07h.
55:48	XTPR 6
	These bits represent the external task priority for symmetric agent ID 06h.
47:40	XTPR 5
	These bits represent the external task priority for symmetric agent ID 05h.
39:32	XTPR 4
	These bits represent the external task priority for symmetric agent ID 04h.
31:24	XTPR 3
	These bits represent the external task priority for symmetric agent ID 03h.
23:16	XTPR 2
	These bits represent the external task priority for symmetric agent ID 02h.
2-44	Intel® 460GX Chipset Software Developer’s Manual