Electrical Specifications
Figure 2.
VCC Overshoot Example Waveform
Example Overshoot Waveform
VOS
VID + 0.050
VID
TOS
Time
TOS: Overshoot time above VID
VOS: Overshoot above VID
NOTES:
1.
2.
VOS is measured overshoot voltage.
TOS is measured time duration above VID.
2.5.4
Die Voltage Validation
Overshoot events on the processor must meet the specifications in Table 6 when
measured across the VCC_SENSE and VSS_SENSE lands. Overshoot events that are
< 10 ns in duration may be ignored. These measurements of processor die level
overshoot must be taken with a bandwidth limited oscilloscope set to a greater than or
equal to 100 MHz bandwidth limit.
2.6
Signaling Specifications
Most processor front side bus signals use Gunning Transceiver Logic (GTL+) signaling
technology. This technology provides improved noise margins and reduced ringing
through low voltage swings and controlled edge rates. Platforms implement a
termination voltage level for GTL+ signals defined as VTT. Because platforms implement
separate power planes for each processor (and chipset), separate VCC and VTT supplies
are necessary. This configuration allows for improved noise tolerance as processor
frequency increases. Speed enhancements to data and address busses have caused
signal integrity considerations and platform design methods to become even more
critical than with previous processor families.
The GTL+ inputs require a reference voltage (GTLREF) that is used by the receivers to
determine if a signal is a logical 0 or a logical 1. GTLREF must be generated on the
motherboard (see Table 16 for GTLREF specifications). Termination resistors (RTT) for
GTL+ signals are provided on the processor silicon and are terminated to VTT. Intel
chipsets will also provide on-die termination, thus eliminating the need to terminate the
bus on the motherboard for most GTL+ signals.
22
Datasheet
INTEL [ INTEL ]
