Ground and Reserved Signals

The following are the general types of reserved (RSVD) signals and connection guidelines:

• RSVD – these signals should not be connected
• RSVD_​TP – these signals should be routed to a test point
• _​NCTF – these signals are non-critical to function and should not be connected.

Arbitrary connection of these signals to VCC, VDD2, VSS, or to any other signal (including each other) may result in component malfunction or incompatibility with future processors. Refer to the table below.

For reliable operation, always connect unused inputs or bi-directional signals to an appropriate signal level. Unused active high inputs should be connected through a resistor to ground (VSS). Unused outputs may be left unconnected however, this may interfere with some Test Access Port (TAP) functions, complicate debug probing and prevent boundary scan testing. A resistor should be used when tying bi-directional signals to power or ground. When tying any signal to power or ground the resistor can also be used for system testability. Resistor values should be within ±20% of the impedance of the baseboard trace, unless otherwise noted in the appropriate platform design guidelines.