Specifications

Intel
®
810E2 Chipset Platform
R
Design Guide
123
4.1.6.3. Flight Time Hardware Validation
When a measurement is made on the actual system, T
CO
and flight time do not need T
REF
correction since
these are the actual numbers. These measurements include all of the effects pertaining to the driver-
system interface and the same is true for the T
CO
. Therefore the addition of the measured T
CO
and the
measured flight time must be equal to the valid delay calculated above.
• Changes in flight time due to crosstalk, noise, and other effects.
4.2. Theory
4.2.1. AGTL+
AGTL+ is the electrical bus technology used for the processor bus. This is an incident wave switching,
open-drain bus with external pull-up resistors that provide both the high logic level and termination at
each load. The processor AGTL+ drivers contain a full-cycle active pull-up device to improve system
timings. The AGTL+ specification defines:
• Termination voltage (V
TT
).
• Receiver reference voltage (V
REF
) as a function of termination voltage (V
TT
).
• processor termination resistance (R
TT
).
• Input low voltage (V
IL
).
• Input high voltage (V
IH
).
• NMOS on resistance (R
ONN
).
• PMOS on resistance (R
ONP
).
• Edge rate specifications.
• Ringback specifications.
• Overshoot/Undershoot specifications.
• Settling Limit.
4.2.2. Timing Requirements
The system timing for AGTL+ is dependent on many things. Each of the following elements combine to
determine the maximum and minimum frequency the AGTL+ bus can support:
• The range of timings for each of the agents in the system.
 Clock to output (T
CO
). (Note that the system load is likely to be different from the
“specification” load therefore the T
CO
observed in the system might not be the same as the T
CO
from the specification.)
 The minimum required setup time to clock (T
SU_MIN
) for each receiving agent.
• The range of flight time between each component. This includes:
 The velocity of propagation for the loaded printed circuit board [S
EFF
].
 The board loading impact on the effective T
CO
in the system.
• The amount of skew and jitter in the system clock generation and distribution.
• Changes in flight time due to crosstalk, noise, and other effects.