AMD SC1201, SC1200 manual Clock Registers, Clock Generator Configuration

General Configuration Block 32579B

4.5.7Clock Registers

The clock generator and PLL registers are described in Table 4-8.

Table 4-8. Clock Generator Configuration

Bit	Description
Offset 10h	Maximum Core Clock Multiplier Register - MCCM (RO)	Reset Value: Strapped Value

This register holds the maximum core clock multiplier value. The maximum clock frequency allowed by the core, is the Fast-PCI clock multiplied by this value.

7:4	Reserved.
3:0	MCM (Maximum Clock Multiplier). This 4-bit value is the maximum multiplier value allowed for the core clock generator. It
	is derived from strap pins CLKSEL[3:0] based on the multiplier value in Table 4-7 on page 85.
Offset 11h		Reserved - RSVD
Offset 12h		PLL Power Control Register - PPCR	(R/W)	Reset Value: 2Fh
This register controls operation of the PLLs.
7	Reserved.
6	EXPCID (Disable External PCI Clock).
	0: External PCI clock is enabled.
	1: External PCI clock is disabled.
5	GPD (Disable Graphic Pixel Reference Clock).
	0: PLL2 input clock is enabled.
	1: PLL2 input clock is disabled.
4	Reserved.
3	PLL3SD (Shut Down PLL3). AC97 codec clock.
	0: PLL3 is enabled.
	1: PLL3 is shutdown.
2	FM1SD (Shut Down PLL4).
	0: PLL4 is enabled.
	1: PLL4 is shutdown, unless internal Fast-PCI clock is strapped to 48 MHz.
1	C48MD (Disable SuperI/O and USB Clock).
	0: USB and SuperI/O clock is enabled.
	1: USB and SuperI/O clock is disabled.
0	Reserved. Write as read.
Offset 13h-17h		Reserved - RSVD
Offset 18h-1Bh		PLL3 Configuration Register - PLL3C	(R/W)	Reset Value: E1040005h
31:24	MFFC (MFF Counter Value).
	Fvco	= OSCCLK * MFBC / (MFFC * MOC)
	OSCCLK = 27 MHz
23:19	Reserved. Write as read.
18:8	MFBC (MFB Counter Value).
	Fvco	= OSCCLK * MFBC / (MFFC * MOC)
	OSCCLK = 27 MHz
	Note:	Bits 18, 9, and 8 cannot be changed. Bit 18 is always a 1; bits 9 and 8 are always 0.
7	Reserved. Write as read.
6	Reserved. Must be set to 0.
5:0	MOC (MO Counter Value).
	Fvco	= OSCCLK * MFBC / (MFFC * MOC)
	OSCCLK = 27 MHz

AMD Geode™ SC1200/SC1201 Processor Data Book 87