Fusion 878A
2.0 Functional Description
PCI Video Decoder
2.14 Multifunction Arbiter
100600B
Conexant
2-49
2.14.3 Interfacing with Non-PCI 2.1 Compliant Core Logic
A small percentage of core logic devices may start a bus transaction during the
same cycle that GNT is de-asserted. This is non PCI 2.1 compliant. To ensure
compatibility when using PCs with these PCI controllers, the EN_VSFX bit must
be enabled (refer to
). When in this mode, the
arbiter does not pass GNT to the internal functions unless REQ is asserted. This
prevents a bus transaction from starting the same cycle when GNT is de asserted.
This also has the side effect of not being able to take advantage of bus parking,
thus lowering arbitration performance. The Fusion 878A drivers must query for
these non-compliant devices, and set the EN_VSFX bit only if required.