Intel 4 620 JM80547PG0722MM Data Sheet

20

All RESERVED signals must remain unconnected. Connection of these signals to V

CC

, V

SS

, V

TT, 

or to any other signal (including each other) can result in component malfunction or 
incompatibility with future processors. See 

 for a land listing of the processor and the 

location of all RESERVED signals.

For reliable operation, always connect unused inputs or bidirectional signals to an appropriate 
signal level. In a system level design, on-die termination has been included on the Pentium 4 
processor to allow signals to be terminated within the processor silicon. Most unused GTL+ inputs 
should be left as no connects, as GTL+ termination is provided on the processor silicon. However, 
see 

 for details on GTL+ signals that do not include on-die termination. Unused active 

high inputs should be connected through a resistor to ground (V

SS

). Unused outputs can be left 

unconnected; however, this may interfere with some test access port (TAP) functions, complicate 
debug probing, and prevent boundary scan testing. A resistor must be used when tying 
bidirectional signals to power or ground. When tying any signal to power or ground, a resistor will 
also allow for system testability. For unused GTL+ input or I/O signals, use pull-up resistors of the 
same value as the on-die termination resistors (R

TT

). Refer to 

 for more details.

TAP, GTL+ Asynchronous inputs, and GTL+ Asynchronous outputs do not include on-die 
termination. Inputs and used outputs must be terminated on the system board. Unused outputs may 
be terminated on the system board or left unconnected. Note that leaving unused outputs 
unterminated may interfere with some TAP functions, complicate debug probing, and prevent 
boundary scan testing. 

FCx signals are signals that are available for compatibility with other processors. Contact your 
Intel representative for further details and documentation.

The TESTHI signals must be tied to the processor V

TT

 using a matched resistor, where a matched 

resistor has a resistance value within ±20% of the impedance of the board transmission line traces. 
For example, if the trace impedance is 60

Ω, then a value between 48 Ω and 72 Ω is required. 

The TESTHI signals may use individual pull-up resistors or be grouped together as detailed below. 
A matched resistor must be used for each group:

•

TESTHI[1:0]

•

TESTHI[7:2]

•

TESTHI8 – cannot be grouped with other TESTHI signals

•

TESTHI9 – cannot be grouped with other TESTHI signals

•

TESTHI10 – cannot be grouped with other TESTHI signals

•

TESTHI11 – cannot be grouped with other TESTHI signals

•

TESTHI12 – cannot be grouped with other TESTHI signals

•

TESTHI13 – cannot be grouped with other TESTHI signals

The FSB signals have been combined into groups by buffer type. GTL+ input signals have 
differential input buffers that use GTLREF as a reference level. In this document, the term “GTL+ 
Input” refers to the GTL+ input group as well as the GTL+ I/O group when receiving. Similarly, 
“GTL+ Output” refers to the GTL+ output group as well as the GTL+ I/O group when driving.