450NX Datasheet, PDF (119/248 Pages) Intel Corporation – Intel 450NX PCIset

11.2 System Reset
Soft Reset
A Soft Reset is a reset directed to the processors on the system bus which does not affect the
configuration or transaction state of the Intel 450NX PCIset or the dependent PCI buses. To
support this function, the system design must externally combine the MIOC’s INIT# output
with the I/O port 92h and keyboard controller soft reset sources as shown in Figure 11-5.
KBC RESET#
I/O Port 92 Reset
MIOC INIT#
Vcc
74F07
INIT# (to processors)
Figure 11-5: Soft Reset
PXB Reset
A PXB Reset is a software-initiated reset that affects only a single PXB and its dependent PCI
buses. Figure 11-4 illustrates a software-initiated PXB Reset.
Reset Without Disturbing PCI Clocks
PCICLKA and PCICLKB must be re-phased whenever any type of reset is asserted if the Intel
450NX PCIset is to be deterministic relative to that reset. The behavior of these clocks cannot
be guaranteed during this re-phasing. A bit in the PXB RC register can be cleared by a
configuration write to defeat the PCI clock re-phasing, so that PCICLKA and PCICLKB remain
well behaved through resets.
11.2.2 Output States During Reset
The following tables shows the signal states of the Intel 450NX PCIset components during a
Power-Good Reset or System Hard Reset. Inputs are denoted by “-”.
Intel® 450NX PCIset
11-5