[SI-LIST] : Time to Vm correction factor

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From: Suchitha.V@smartm.com
Date: Fri Feb 09 2001 - 10:18:44 PST


      
Hello All,

                    This question is related to the load conditions used to
determine the
                     TIME-TO-VM correction factor for the Mobile Pentium III
processor and
                     the 82443BX chipset.
                     I understand that the load conditions mentioned in the
model to
                     determine the TIME-TO VM correction should be the same
as that
                     mentioned in the datasheets for a particular component.

                     The GTL model for the 82443BX has the following load
conditions in
                     the model
                     TIME_TO_VM: 1.22 0.31 # C=0 pF, R=25 Ohms, V=1.5 V,
Vmeas=1 V
                     This is the same load conditions as mentioned in the
datasheets

                     The GTL model for Mobile P III with 50 ohm on-die
termination (FAST
                     MODEL) has the following load conditions in the model
                     TIME_TO_VM: 0.36 0.29 # C=0 pF,R=1e+007 Ohms,V=0V
Vmeas=1.076 V

                     As per the datsheets in Mobile PentiumŪ III Processor
in BGA2 and
                     Micro-PGA2 Packages at 400 MHz, 450 MHz, and 500 MHz
Datasheet
                     Table 15. GTL+ Signal Groups AC Specifications
                     RTT = 56W internally terminated to VCCT; VREF =2/3VCCT;
load = 0 pF;

                     AS per the 82443BX Host Bridge/Controller - Timing
Specification
                     Mobile delays are specified into a 56 ohm resistor
which is tied to VTT=1.5V

                     Why has the Time to Vm calculated with R=10 Megaohms
tied to V=0V in the model?
                     Why has such a high value of resistor being used?
                     Shall i calculate the Time to Vm specified in the
datasheets
                     that is with R=56ohms tied to V=1.5V, C=0pF, and
Vmeas=1V ?

                     Looking forward to your replies and suggestions.
                     Suchitha
                   

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