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13-1
CHAPTER 13
3.3V TOLERANT SIGNAL QUALITY
SPECIFICATIONS
The signals that are 3.3V tolerant should also meet signal quality specifications to guarantee that
the components read data properly and to ensure that incoming signals do not affect the long
term reliability of the component. There are three signal quality parameters defined for the 3.3V
tolerant signals. They are Overshoot/Undershoot, Ringback and Settling Limit. All three signal
quality parameters are shown in Figure 13-1. The Pentium
®
Pro Processor I/O Buffer Mod-
els—IBIS Format (on world wide web page www.intel.com) contain models for simulating 3.3V
tolerant signal distribution.
13.1.
OVERSHOOT/UNDERSHOOT GUIDELINES
Overshoot (or undershoot) is the absolute value of the maximum voltage allowed above the nom-
inal high voltage or below VSS. The overshoot/undershoot guideline limits transitions beyond
VCCP or VSS due to the fast signal edge rates. See Figure 13-1. The processor can be damaged
by repeated overshoot events on 3.3V tolerant buffers if the charge is large enough (i.e. if the
overshoot is great enough). However, excessive ringback is the dominant harmful effect result-
ing from overshoot or undershoot (i.e. violating the overshoot/undershoot guideline will make
satisfying the ringback specification difficult). The overshoot/undershoot guideline is 0.8V
and assumes the absence of diodes on the input. These guidelines should be verified in simula-
tions without the on-chip ESD protection diodes present because the diodes will begin clamp-
ing the 3.3V tolerant signals beginning at approximately 1.5V above VCCP and 0.5V below
VSS. If signals are not reaching the clamping voltage, then this is not an issue. A system should
not rely on the diodes for overshoot/undershoot protection as this will negatively affect the life
of the components and make meeting the ringback specification very difficult.
Summary of Contents for Pentium Pro Family
Page 17: ...1 Component Introduction ...
Page 26: ...2 Pentium Pro Processor Architecture Overview ...
Page 27: ......
Page 36: ...3 Bus Overview ...
Page 62: ...4 Bus Protocol ...
Page 105: ...5 Bus Transactions and Operations ...
Page 126: ...6 Range Registers ...
Page 131: ...7 Cache Protocol ...
Page 135: ...8 Data Integrity ...
Page 148: ...9 Configuration ...
Page 161: ...10 Pentium Pro Processor Test Access Port TAP ...
Page 172: ...11 Electrical Specifications ...
Page 201: ...12 GTL Interface Specification ...
Page 229: ...13 3 3V Tolerant Signal Quality Specifications ...
Page 233: ...14 Thermal Specifications ...
Page 239: ...15 Mechanical Specifications ...
Page 241: ...15 2 MECHANICAL SPECIFICATIONS s Figure 15 1 Package Dimensions Bottom View ...
Page 252: ...16 Tools ...
Page 260: ...16 8 TOOLS Figure 16 4 Generic MP System Layout for Debug Port Connection ...
Page 264: ...17 OverDrive Processor Socket Specification ...
Page 290: ...A Signals Reference ...
Page 320: ...Index ...
Page 328: ......