| OnNow is based on the ACPI power management
scheme. In order to understand how OnNow works and what role ACPI plays in this, we will
first explain some concepts of ACPI. Under ACPI, there are 4 distinctive power states: G0, the working
state, G1 the sleeping state, G2 the softpower off state and G3, the mechanical off state.
The G1 state is where OnNow plays its part.
The G1 state contains 4 distinctive sleeping modes S1, S2, S3, S4.
S1: (standby 1) low latency (= quick to wake
up)
system and CPU clocks are stopped, system context is still in its original state
S2: (standby 2) low latency
system and CPU clocks are stopped, CPU and cache are powered off and their data is placed
into the memory.
S3: (suspend-to-memory = OnNow) low latency
All board components except the memory are powered off, CPU and cache data are placed in a
reserved area of the memory and retrieved after wake-up.
S4: (suspend-to-disk) high latency
All board components are powered off, CPU/cache/memory data are placed on the harddisk and
retrieved after wake-up.
The OnNow state requires the mainboard to be
able to switch off the power to all onboard components except the memory. Current
mainboards do not have this separation of onboard powersupply. OnNow ready mainboards will
therefore require a more complex design for the mainboard's powersupply. The system
powersupply will also need to support OnNow in order to make suspend-to-memory work.
Chaintech supports the OnNow initiative
wholeheartedly and is busy implementing OnNow technology into a new generation of
Chaintech mainboards. |
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