ST486DX ST Microelectronics, ST486DX Datasheet - Page 29

• Manufacturer Part Number: ST486DX
• Description: PROGRAMMING MANUAL
• Manufacturer: ST Microelectronics

4.
The SGS-Thomson CPU provides several methods and levels of power management. The fully
static design allows clock stopping. Suspend Mode, SMM and 3.3 volt operation can be used to
achieve optimum CPU and system power management. Table 4-1 summarizes the various power
management options for the SGS-Thomson CPU.
4.1
The SGS-Thomson CPU is a fully static design meaning the input clock frequency can be reduced
or stopped without a loss of internal CPU data or state. The system designer can make decisions to
reduce the clock frequency by using SGS-Thomson SMM capabilities, Advanced Power Manage-
ment (APM) software API and/or chipset capabilities. When the clock is removed and then reas-
serted, execution will begin with the instruction where the clock was removed from the CPU.
4.2
SGS-Thomson CPUs are available that operate at either 3.3 or 5.0 volts. Parts rated at 3.3 volts
have the letter ’V’ included in the part number (Refer the appropriate SGS-Thomson data book for
complete ordering information). The typical current (I
duced by approximately 50% when operating at 3.3 instead of 5.0 volts. Operating the CPU at 3.3
volts can reduce CPU power consumption by over 70%, as the power consumption increases as the
square of the power supply voltage (P-=-V
Table 4 - 1
Note: Values listed are approximations. Refer to the appropriate SGS-Thomson data book for DC specifications.
Reduced Clock Frequency
5.0V operation
3.3V operation
Remove Clock
Suspend Mode clock operating
Suspend Mode and Remove Clock
Remove Power
Power Management Features
Reducing the Clock Frequency
Lowering the CPU Supply Voltage
Power Management Options
Option
ST486DX - SMM POWER MANAGEMENT FEATURES
2
/R and P-=-CV
(13 x f
610 mA @ 33 MHz, 765 mA @ 50 MHz
360 mA @ 33 MHz
150 mA
15 mA
450 A
0 mA
cc
) drawn by the SGS-Thomson CPU is re-
CLK
2
F).
(MHz)) + 150 mA @ 5.0 V
Typical Curr ent Options
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