Thermals; Thermtrip# Requirements; Thermtrip# Erratum - Intel Pentium III Processor 512K Design Manual

® ®
LV Intel Pentium III Processor 512K Dual Processor Platform
6.0

Thermals

The LV Intel Pentium
Please refer to the Low Voltage Intel
more information.
6.1

THERMTRIP# Requirements

In the event the processor drives the THERMTRIP# signal active during valid operation, both the
Vcc and Vtt supplies to the processor must be powered off to prevent thermal runaway of the
processor. Valid operation refers to operating conditions in which the THERMTRIP# signal is
guaranteed valid. The time required from THERMTRIP# assertion to V
5 seconds; the time required from THERMTRIP# assertion to V
Table 19. THERMTRIP# Timing Requirements
6.2

THERMTRIP# Erratum

Intel has identified an issue with THERMTRIP# which may incorrectly assert during de-assertion
of RESET# at nominal operating temperatures in LV Intel Pentium
processors. The assertion of THERMTRIP# with cause the processor to shut down internally and
stop execution. This issue can lead to intermittent system power-on boot failures.
To prevent the risk of power-on boot failures a platform workaround is required. The system must
provide a rising edge on the TCK signal during the power-on sequence that meets all of the
following requirements:
•
Edge occurs after Vcc
•
Edge occurs before or at the de-assertion of RESET#
•
Edge occurs after all V
•
TCK input meets the Vih
Pentium
Specific workaround implementations may be platform specific. The following example has been
tested as a acceptable workaround implementation.
The example workaround circuit, shown in Figure 23, requires circuit modifications for ITP tools
to function correctly. These modifications must remove the workaround circuitry from the platform
and may cause systems to fail to boot. Issuing the ITP 'Reset Target' command on failing systems
will reset the system while providing a sufficient rising edge on the TCK pin to ensure system boot.
The example workaround circuit (shown in Figure 23) does not support production motherboard
test methodologies that require the use of the processor JTAG/TAP port. Alternative workaround
solutions must be found if such test capability is required.
38
processor 512K requires a robust thermal solution for proper operation.
III
®
Power Rail
V
CC
V
TT
is valid and stable
CORE
input signals are at valid voltage levels
ref
and Vih
min
®
III Processor 512K Datasheet.
Pentium Processor 512K (DP) Thermal Design Guide for
III
Power Target
1/2 Nominal V
CC
1/2 Nominal V
TT
spec requirements of the Low Voltage Intel
max
rail at 1/2 nominal is
CC
rail at 1/2 nominal is 5 seconds.
TT
Time Required for Power Drop
5.0 seconds
5.0 seconds
III processor 512K A-1 stepping
®
Design Guide