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OVERDRIVE® PROCESSOR SOCKET SPECIFICATION
17.3.3.1.
OVERDRIVE
Following power-on RESET or the CPUID instruction, the EAX register contains the values
shown in Table 17-3.
Type [13:12]
1
17.3.3.2.
COMMON CAUSES OF UPGRADABILITY PROBLEMS DUE TO BIOS
CPU signature detection has been a common cause of current upgradability problems due to
BIOS. A few precautions within the BIOS can help to eliminate future upgradability problems
with Pentium Pro processor-based systems. When programming or modifying a BIOS, be aware
of the impact of future OverDrive processors. The following recommendations should prevent
problems in the future:
•
Always use the CPU signature and feature flags to identify the processor, including future
processors.
•
Never use timing loops for delays.
•
If an OverDrive processor is detected, report the presence of an "OverDrive processor" to
the end-user.
•
If an OverDrive processor is detected, don't test on-chip cache sizes or organization. The
OverDrive processor cache parameters differ from those of the Pentium Pro processor.
•
If an OverDrive processor is detected, don't use the Pentium Pro processor model specific
registers and test registers. OverDrive processor MSRs differ from those of the Pentium
Pro processor.
•
Memory Type Range Registers must be programmed as for a Pentium Pro processor.
17.4.
OVERDRIVE
SPECIFICATIONS
This section describes the electrical requirements for the OverDrive processor.
ZIF socket electrical parameters may differ from LIF socket parameters;
therefore, be sure to use the appropriate ZIF socket parameters for electrical
design simulations.
17-14
®
PROCESSOR CPUID
®
Table 17-3. OverDrive
Family [11:8]
6
®
PROCESSOR ELECTRICAL
NOTE
Processor CPUID
Model [7:4]
3
Stepping [3:0]
X
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