AMD 8151 specifications Clock Control Register, Bits Description

24888 Rev 3.03 - July 12, 2004AMD-8151TMAGP Tunnel Data Sheet

6:5	ACTL: link side A PHY control value. Read-write. These two bits combine to specify the PHY
	compensation value that is applied to side A of the tunnel as follows:
	ACTL	Description
	00b	Apply CALCCOMP directly as the compensation value.
	01b	Apply ADATA directly as the compensation value.
	10b	Apply the sum of CALCCOMP and ADATA as the compensation value. In
		DevA:0x[E4, E0], if the sum exceeds 13h, then 13h is applied. In DevA:0x[E8], if the
		sum exceeds 1Fh, then 1Fh is applied.
	11b	Apply the difference of CALCCOMP minus ADATA as the compensation value. If the
		difference is less than 01h, then 01h is applied.
	The default value of this field (from PWROK reset) is controlled by the CMPOVR signal. If
	CMPOVR = 0, the default is 00b. If CMPOVR = 1, the default is 01b.
4:0	ADATA: link side A data value. Read-write. This value is applied to the side A of the tunnel PHY
	compensation as described in ACTL. The default for DevA:0x[E4, E0] is 08h. The default for
	DevA:0xE8 is 0Fh.
Clock Control Register			DevA:0xF0

See section 4.3.1 for details on clock gating. AMD system recommendations for System Management Action Field (SMAF) codes are: 0=ACPI C2; 1=ACPI C3; 2=FID/VID change; 3=ACPI S1; 4=ACPI S3; 5=Throt- tling; 6=ACPI S4/S5. For server and desktop platforms, AMD recommends setting this register to 0004_0008h (to gate clocks during S1). For mobile platforms, AMD recommends setting this register to 0004_0A0Ah (to gate clocks during C3 and S1).

Default: 0000 0000h. Attribute: Read-write.

Bits Description

31:19 Reserved.

18CGEN: clock gate enable. 1=Internal clock gating, as specified by bits[7:0] of this register, is enabled.

17Must be low. This bit is required to be low at all times; setting it high results in undefined behavior.

16Must be low. This bit is required to be low at all times; setting it high results in undefined behavior.

15:8	ECGSMAF: external clock gating system management action fields. Each of the bits of this field
	correspond to SMAF values that are captured in Stop Grant cycles from the host. For each bit,
	1=When LDTSTOP# is asserted prior to a Stop Grant cycle in which the SMAF field matches the
	ECGSMAF bit that is asserted, then A_PCLK and internal clock grids associated with the AGP
	bridges are forced low. 0=A_PCLK and the internal clock grids are active while LDTSTOP# is
	asserted. For example, if A_PCLK gating is required for SMAF values of 3 and 5, then ECGSMAF[3,
	5] must be high. See section 4.3.1 for details.
7:0	ICGSMAF: internal clock gating system management action fields. Each of the bits of this field
	correspond to SMAF values that are captured in Stop Grant cycles from the host. For each bit,
	1=When LDTSTOP# is asserted prior to a Stop Grant cycle in which the SMAF field matches the
	ICGSMAF bit that is asserted, then the IC power is reduced through gating of internal clocks. 0=No
	power reduction while LDTSTOP# is asserted. For example, if clock gating is required for SMAF
	values of 3 and 5, then ICGSMAF[3, 5] must be high. See section 4.3.1 for details.
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