Accelerated Graphics Port Interface Specification

AGP3.0 Interface Specification

Rev. 1.0

2.6 Register Table Format

Each Register is specified using the following format:

Table 21: Register Description

Bits Access Field Description

HighBit : LowBit

(Zero-origin)

<ACCESS> Name Description

Bit (Zero-origin) <ACCESS> Name Description

The ACCESS column is of the form:

[READ] – [WRITE] – [DEFAULT] Table 22 defines the value of each sub-field:

Table 22: Sub-field Values

Field Value Meaning

[READ]

R Read Allowed

RZ Always Read-as-Zero

R1 Always Read-as-One

-- Read not allowed

[WRITE]

W Write Allowed

W1C Write of any value clears to zero

IW Writes Ignored

MW Must Write back what is Read (Write-Under-Mask)

-- Write not allowed

[DEFAULT]

D’0 Power-on-Default is Zero

D’1 Power-on-Default is One

Dx Power-on-Default is not specified by AGP3.0

D’?? Power-on-Default needs to be specified.

D’xxxx Power-on-Default is xxxx

-- Hardwired-Value doesn’t need Power-on-default