641 datasheet(22/106 Pages) INTEL

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Electrical Specifications

Datasheet

NOTES:

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.

Figure 2.

VCC Overshoot Example Waveform

Time

Example Overshoot Waveform

VID

VID + 0.050

OS: Overshoot time above VID

OS: Overshoot above VID

641 Datasheet(PDF) 22 Page - Intel Corporation