Intel CONTROLLERS 413808 - Manual (Page 133)

Intel ® 413808 and 413812 I/O Controllers in TPER Mode
October 2007 Developer’s Manual
Order Number: 317805-001US 133
Address Translation Unit (PCI-X)—Intel
®
413808 and 413812
2.12.5 External Clock Driver (CR_FREQ[1:0])
When the internal PCI Clock outputs are not sufficient, an external clock driver can be
used to supply additional PCI Clocks. To facilitate the use of an external driver, the
CR_FREQ[1:0] pins are driven based on the settings in the PCI-X capability field (bits
19:16) in the “PCI Configuration and Status Register - PCSR” . These output pins can be
connected to a PCI-X clock driver to select the desired bus frequency.
Table 22. CR_FREQ[1:0] Encoding
PCSR[19:16]
(PCIX Init
Pattern)
PCSR[10]
(P_M66EN)
CR_FREQ[1:0] Bus Frequency Bus Mode
1111 0 11 33 MHz Conventional PCI
1111 1 10 66 MHz Conventional PCI
1110 - 10 66 MHz PCI-X
1101 - 01 100 MHz PCI-X
1100 - 00 133 MHz PCI-X