System solution to allow 64-bit PCI adapters to determine state during reset

摘要

A modified system causes the REQ64# signal to be asserted when the adapter is in reset on a 64-bit slot. This allows the adapter to see that it is in a 64-bit slot at the beginning of reset, preventing the adapter from driving the 64-bit extension pins. The above-described modification must be made to all the 64-bit slots on a system. When the reset signal is active, it will cause the buffer to drive the REQ64# signal low. This will synchronize reset and REQ64#, eliminating the possibility for bus contention. No modification is necessary for 32-bit slots. This modification will not affect the normal operation of the bus, since it is only used during reset.