Bob said:
In XP is the sleep mode the same as hybernate? Is the computer actually
shut off? If not is there a way to do this so it remembers your screen
configuration on wake-up?
Thanks in advance... Bob
S3 Suspend To RAM, involves the session remaining in RAM. The
main power supply rails are turned off. The fans stop spinning.
The +5VSB supply continues to operate. It supplies power to the RAM.
The RAM is refreshing itself (DRAM does that to maintain its contents).
On a restart, a mini-restart of the drivers is needed, so that the
hardware state can be restored. Since the main power supply rails
were turned off, the PCI cards don't remember everything they need to
work. So there are no guarantees about a lot of the hardware state,
which is why the drivers have to "warm start" things.
S4 Hibernate, involves writing something into the Hiberfile. On
recovery from Hibernate, the contents of the Hiberfile are used
to load up the RAM. It is not clear to me at least, how this process
works. There seem to be side effects, once the recovered session
starts running, as if the write out was done by flushing virtual
memory or something. In any case, S4 Hibernate is not reliant on
any hardware remembering what is going on. If you switch off the
computer at the back, while it is hibernating, since the session
is stored on disk, it is possible to recover later. So while
+5VSB may be running during Hibernate, the whole concept is not
reliant on anything that might be using the +5VSB at the time.
S3, on the other hand, is relying on the RAM remaining powered.
If the computer loses AC power while in S3, it will have to
do a fresh reboot when the power is restored.
S3 is not the same as S4. In S4, if they wanted, they could
configure the hardware to draw less power from +5VSB. But there
is no mechanism for the OS to turn off all the power in S4, as
inviting as that might seem. To turn off +5VSB, requires use
of the mechanical switch on the back of the PC.
+5VSB can supply around 1 amp, while the computer is in S3 or S4.
(The supply has a higher capacity, but that might be a guess
at the amount actually needed by the motherboard.) Since the
conversion process inside the supply, is not very efficient
for that particular rail, the power supply might actually draw
10 watts from the wall, in order to make 5 watts on the +5VSB output.
The rest is released as heat inside the supply (which is why
the exhaust is warm instantly, when you start up). The exact
values involved, may differ from one computer design to another.
I believe there are some pre-built computers, which have
achieved better standby figures. The numbers I quote
above, may be what a user who builds their own computer
might see. Some pre-built computers may do better than
that.
Switching off at the back, or unplugging, is the only way to
get the power consumed, to zero. And even then, perhaps
10 microwatts is being drawn from the CMOS battery, to
power the real time clock (RTC). In such a situation,
S4 Hibernate is what you want, to remember the session.
Paul
