Do I need a rear fan?

[casey.o]

The computer I'm working on is an unknown brand. No where on the case
is any name. The processor is AMD Athlon 64 processor 3200+ 2G of ram.
The harddrive is a SATA type. Asus motherboard.

I got this computer complete, except that rear fan was missing, as well
as no hard drive or floppy drive. I got a hard drive, adn plan to get a
floppy, but I'm wondering if that rear fan is needed? There is the fan
in the power supply, and a CPU cooler fan on the CPU. That is all I
have on my older computers, but it seems these newer high powered types
all have a rear fan. Do I need one? I should mention that I rarely
keep the cover on the case in any computer, so that makes me even more
question the need for that fan.

Right now, it's cool in the house, (about 60deg) so I'm not too worried
about overheating, but when hot weather comes, will I need this fan?

 

[Mayayana]

| Right now, it's cool in the house, (about 60deg) so I'm not too worried
| about overheating, but when hot weather comes, will I need this fan?
|
It doesn't hurt to get another fan. They're less
than $10. But if you can't plug it into the board --
if you have to power it direct -- then it won't turn
off when you go to standby. The noise could also
bother you.

You could keep an eye on the heat levels, though
that won't tell you about the hard disk(s).

One thing I like to do, either way, is to get a
cheap blanket type air filter and cut it up for
use on the intakes. Over time a lot of dust can
accumulate in a well vented box. If you put
low-resistance filter material over the intakes
you can avoid that.

 

[Jeff Barnett]

Mayayana wrote, On 3/28/2014 7:51 AM:

| Right now, it's cool in the house, (about 60deg) so I'm not too worried
| about overheating, but when hot weather comes, will I need this fan?
|
It doesn't hurt to get another fan. They're less
than $10. But if you can't plug it into the board --
if you have to power it direct -- then it won't turn
off when you go to standby. The noise could also
bother you.

You could keep an eye on the heat levels, though
that won't tell you about the hard disk(s).

One thing I like to do, either way, is to get a
cheap blanket type air filter and cut it up for
use on the intakes. Over time a lot of dust can
accumulate in a well vented box. If you put
low-resistance filter material over the intakes
you can avoid that.

Whether a fan turns off or not depends on what state is used for sleep,
i.e., S2, S3, hibernate, etc., and the type of power supply. For
example, my XP PRO SP3 machines use S3 sleep and hibernates in case of
power failure; some fans are plugged to the motherboard and some
directly to the power supply. S2 state could leave fans running. So it
depends on many things, none of which were specified by the original poster.

Jeff Barnett

 

[Bob F]

It doesn't hurt to get another fan. They're less
than $10. But if you can't plug it into the board --
if you have to power it direct -- then it won't turn
off when you go to standby. The noise could also
bother you.

You could keep an eye on the heat levels, though
that won't tell you about the hard disk(s).

One thing I like to do, either way, is to get a
cheap blanket type air filter and cut it up for
use on the intakes. Over time a lot of dust can
accumulate in a well vented box. If you put
low-resistance filter material over the intakes
you can avoid that.

I'd suggest setting up Speedfan or a similar program so you can see the temps of
processors and GPUs. That way tou can make a decision based on real data.

If OP does not replace the rear fan, I'd advise taping over the area it goes so
that air cannot come in through that space and exhaust out through the power
supply, thereby short-circuiting the air form that might otherwise come from the
front of the box, thereby cooling the GPU, grives, etc.

I recently built a "new" PC and designed it to exhaust hot air from the
processor and GPU directly, using baffles to direct the hot air directly from
the processor to the power supply fan, and building a posterboard case around
the HD4850 X2 video card, which exhaust all the air from the fans on that card
directly through a 1" x 12" slot I cut in the case cover directly above the
card. I also removed the 5 1/4" drive slot covers at the front of the case for
air input, and taped over all other holes where air could enter. This thing runs
really cool. In my 60 F room, the Q6600 cores are at in the mid 40's C and the
GPU only slightly warmer, with the fans running almost inaudibly.

The fans do speed up if the PC is worked harder, and I found that even fairly
limited air filtering (2/3 sq ft of 1/4" porous foam) causes it to cycle more
often. I'd like to find a quiet 5" fan to run slowly in the 3 drive bays the air
comes in through so I can filter the air better without the noise.

 

[Mayayana]

| Whether a fan turns off or not depends on what state is used for sleep,
| i.e., S2, S3, hibernate, etc., and the type of power supply.

I said standby, which seems to be "S3". I'm not aware of
other choices than hibernate in XP. Interesting point, though.
I didn't think of hibernate as I've never enabled it because
it takes so much memory.

| For
| example, my XP PRO SP3 machines use S3 sleep and hibernates in case of
| power failure; some fans are plugged to the motherboard and some
| directly to the power supply. S2 state could leave fans running. So it
| depends on many things, none of which were specified by the original
poster.
|

So are you saying that some PCs with fans wired
straight to the power supply will shut off in standby?
I've never heard of different kinds of power supplies
in that regard.... or in any other, actually, other
than wattage.

 

[Paul]

The computer I'm working on is an unknown brand. No where on the case
is any name. The processor is AMD Athlon 64 processor 3200+ 2G of ram.
The harddrive is a SATA type. Asus motherboard.

I got this computer complete, except that rear fan was missing, as well
as no hard drive or floppy drive. I got a hard drive, adn plan to get a
floppy, but I'm wondering if that rear fan is needed? There is the fan
in the power supply, and a CPU cooler fan on the CPU. That is all I
have on my older computers, but it seems these newer high powered types
all have a rear fan. Do I need one? I should mention that I rarely
keep the cover on the case in any computer, so that makes me even more
question the need for that fan.

Right now, it's cool in the house, (about 60deg) so I'm not too worried
about overheating, but when hot weather comes, will I need this fan?

Yes, you need a fan on the back.

*******

You need a fan on the back, because there is a cloud of
warm air around the CPU socket. And the power supply fan
typically does not move enough cubic feet per minute to
cool it. The PSU is not a cabinet cooler.

Cabinet cooling equation...

CFM = 3.16 * Watts / Delta_T_degrees_F

You can measure the computer power consumption with a Kill-O-Watt
meter. You measure that power consumption, while the CPU is 100%
busy (as seen in Task Manager). A Kill-O-Watt meter is relatively
cheap ($20 right now, maybe up to $35).

http://www.amazon.com/P3-International-P4400-Electricity-Monitor/dp/B00009MDBU

Let's say the room is 25C and you want to limit the inside
of the computer to 35C. That's a 10C difference or 18F degrees.
Say the computer is a bit of a pig and uses 200W of power at
its peak.

CFM = 3.16 * 200 / 18 = 35CFM

And 35CFM would be a 120mm or 80mm typical case fan from
the computer store. You'd probably want something a little
faster and noisier than a Vantec Stealth in that example.
I use Stealth here, but they don't "feel" like a 35CFM fan.
Probably a bit less. Fans come in four "speeds" if you will,
and the two bottom speeds are quiet, the two top ones noisy.
You'd want the second from the bottom in terms of cooling
performance, to cool that 200W load.

*******

Speedfan will help you, as long as the fan header is speed
controlled. Asus motherboards are not very generous in that
regard. Lowest tier motherboards, the CPU fan is the only
one with speed control. Enthusiast motherboards, may have
a second chassis fan header which is speed control equipped.

A number of HP (OEM) computers, all the headers are speed controlled.

There is no hardware status indicator, to show that the
necessary transistor is present to control the voltage to
the fan header. If you use SpeedFan, it will see the three
channels of "fan control", but those don't work unless the
transistor and electrolytic cap are present next to the fan
header. To save money, they don't install them. You can
"dial the control" in SpeedFan, and a header lacking the
circuit, will cause the fan to continue to run at full speed.
There is no harm dialing the speed in SpeedFan, when the
transistor is missing, and when the fan speed doesn't change,
that's how you verify the information provided in the
motherboard manual.

So don't expect miracles.

The best compromise, would be to buy a Vantec Stealth 80mm or
120mm, let it run full speed... and expect the inside of the
computer case to get a little warm when it is 35C inside the
house in summer.

The other question you should be asking, is why we cool
the computer case. Primarily, it's to protect the hard drive.
We're trying to prevent the hard drive from going above 50C.
Other components in the computer, can take slightly more
heat than that, and all that running the computer warm will
do, is reduce the calculated lifetime of the electrolytic
capacitors on the motherboard and inside the ATX PSU.
But for me, the more immediate concern is the hard drive.

The Google hard drive study, claims there is no temperature
effect on drive life. This fails to take into account the
design of the hard drive spindle motor. The spindle bearing
is "filled" with oil and is frictionless as long as oil is present.
Only a single drop of oil is present, and it recirculates
inside the motor bearing (fluid dynamic). The problem is,
at high temperature, the oil tends to escape from the
bearing. The amount of oil is so tiny, engineers at the
disk drive factory detect it is missing, by weighing the
motors on a gram balance (weigh it when filled, then
take the weight later at regular intervals). That's the
only way they can determine it has evaporated, when
lab testing. So when we cool a hard drive, it's a simple
matter of physics, and trying to prevent the oil from
wanting to leave the spindle motor prematurely. You would
think it would make sense to have a rather large oil
tank connected to the motor, but it doesn't work that way

Paul

 

[Jeff Barnett]

Mayayana wrote, On 3/28/2014 11:09 AM:

| Whether a fan turns off or not depends on what state is used for sleep,
| i.e., S2, S3, hibernate, etc., and the type of power supply.

I said standby, which seems to be "S3". I'm not aware of
other choices than hibernate in XP. Interesting point, though.
I didn't think of hibernate as I've never enabled it because
it takes so much memory.

| For
| example, my XP PRO SP3 machines use S3 sleep and hibernates in case of
| power failure; some fans are plugged to the motherboard and some
| directly to the power supply. S2 state could leave fans running. So it
| depends on many things, none of which were specified by the original
poster.
|

So are you saying that some PCs with fans wired
straight to the power supply will shut off in standby?
I've never heard of different kinds of power supplies
in that regard.... or in any other, actually, other
than wattage.

Above, I meant to add that all my fans shut down in S3 sleep. According
to my UPS, I only draw 3-4 watts while snoozing. This means that the
power supply is cooperating (actively or passively) since all fans, no
matter their connection, are off.

Jeff Barnett

 

[Paul]

Mayayana wrote, On 3/28/2014 11:09 AM:

Above, I meant to add that all my fans shut down in S3 sleep. According
to my UPS, I only draw 3-4 watts while snoozing. This means that the
power supply is cooperating (actively or passively) since all fans, no
matter their connection, are off.

Jeff Barnett

The fans run off +12V typically.

The standby power in the power supply (the "3-4 watt" one), is +5VSB.
And that would not be a preferred source of power for a brushless DC fan.
There is enough loading on that rail already. The PSU is rated for somewhere
between 5VSB @ 2A to 5VSB @ 3A or so. And now people are charging their
iPads from the USB port, while the computer is asleep. That would be
on top of the roughly 1A load the motherboard places on +5VSB for
S3 sleep (powers LAN chip and does memory refresh cycles).

The ATX PSU has two switching converters inside. The +5VSB has its
own switcher. That switcher is expected to make +5VSB, while
there is no fan running inside the PSU to keep it cool.

(+5VSB is the switcher circuit in the lower left corner)
http://www.pavouk.org/hw/en_atxps.html

I have one power supply here, that when the computer is sleeping,
it's doing the +5VSB thing (in other words, perfectly normal). When
you switch on the computer with the button on the front, you can feel
a short burst of warm air come out of the PSU cooling hole - and
this is the elevated air temperature inside that supply, while the +5VSB
runs all night. That circuit gets to run cooler, once both
switchers are running, all the fans spin, and the computer is fully on.

The power supply uses convection cooling for the +5VSB switcher,
while the computer sleeps.

Paul

 

[Mayayana]

| Above, I meant to add that all my fans shut down in S3 sleep. According
| to my UPS, I only draw 3-4 watts while snoozing. This means that the
| power supply is cooperating (actively or passively) since all fans, no
| matter their connection, are off.
|

That's odd. I used to have a rear fan plugged into
a standard 4-wire power socket coming from the
power supply and it kept running during standby.
I assumed that was the norm.

 

[Buffalo]

wrote in message news:[email protected]...

The computer I'm working on is an unknown brand. No where on the case
is any name. The processor is AMD Athlon 64 processor 3200+ 2G of ram.
The harddrive is a SATA type. Asus motherboard.

I got this computer complete, except that rear fan was missing, as well
as no hard drive or floppy drive. I got a hard drive, adn plan to get a
floppy, but I'm wondering if that rear fan is needed? There is the fan
in the power supply, and a CPU cooler fan on the CPU. That is all I
have on my older computers, but it seems these newer high powered types
all have a rear fan. Do I need one? I should mention that I rarely
keep the cover on the case in any computer, so that makes me even more
question the need for that fan.

Right now, it's cool in the house, (about 60deg) so I'm not too worried
about overheating, but when hot weather comes, will I need this fan?

If you don't have the case cover on, it really won't make much difference,
if any.
Even when the case cover is off, you may need a small room fan blowing
lightly across the innards.
A proper case with covers on directs the air flow better.
If you use a free temp monitoring program, such as CPUIDHWMonitor , you will
be able to see several temps, etc.

 

[Paul]

| Above, I meant to add that all my fans shut down in S3 sleep. According
| to my UPS, I only draw 3-4 watts while snoozing. This means that the
| power supply is cooperating (actively or passively) since all fans, no
| matter their connection, are off.
|

That's odd. I used to have a rear fan plugged into
a standard 4-wire power socket coming from the
power supply and it kept running during standby.
I assumed that was the norm.

Monitor off, fans spinning, is S1.

Monitor off, fans off, is S3/S4/S5.

You have to be a bit careful with some of these definitions,
like what does "CPU stopped" mean ? If it means usage of the
Halt instruction, the CPU wakes up immediately on the next
Clock Tick interrupt. Which is no more or no less, than what the
Idle task does for you in the OS. The Idle task uses Halt to save
power, with the CPU waking up many times a second and running
the OS scheduler to see if anything needs to run.

http://www.overclock.net/t/1058894/intel-acpi-guide-c-g-s-p-states-and-ocs

The C states on the other hand, support an unending number of
variations on power saving at the CPU level. On modern systems,
the C states now extend to at least C6. The Wikipedia article claims the
C states extend to C10 for Haswell. Each of these states
is a lower power, with things like the ability to turn off
power on individual cores or the like. Since Haswell has
a power converter inside the CPU, there are a lot more
possibilities in terms of power control. (Something not
addressed in the slide deck describing the Haswell
power converter.)

Paul

 

[Paul in Houston TX]

The computer I'm working on is an unknown brand. No where on the case
is any name. The processor is AMD Athlon 64 processor 3200+ 2G of ram.
The harddrive is a SATA type. Asus motherboard.

I got this computer complete, except that rear fan was missing, as well
as no hard drive or floppy drive. I got a hard drive, adn plan to get a
floppy, but I'm wondering if that rear fan is needed? There is the fan
in the power supply, and a CPU cooler fan on the CPU. That is all I
have on my older computers, but it seems these newer high powered types
all have a rear fan. Do I need one? I should mention that I rarely
keep the cover on the case in any computer, so that makes me even more
question the need for that fan.

Right now, it's cool in the house, (about 60deg) so I'm not too worried
about overheating, but when hot weather comes, will I need this fan?

Only you can determine the number of fans and placement.
Does anything feel hot when running?

This machine that I am using at the moment has 8 fans
and still runs hot:
pwr supply 6"
cpu 4"
chipset 4"
ram 4"
gpu front side 4"
gpu back side 4"
harddrives 4"
comp side panel 12" a/c line powered fan

 

[casey.o]

effect on drive life. This fails to take into account the
design of the hard drive spindle motor. The spindle bearing
is "filled" with oil and is frictionless as long as oil is present.
Only a single drop of oil is present, and it recirculates
inside the motor bearing (fluid dynamic). The problem is,
at high temperature, the oil tends to escape from the
bearing. The amount of oil is so tiny, engineers at the
disk drive factory detect it is missing, by weighing the
motors on a gram balance (weigh it when filled, then
take the weight later at regular intervals). That's the
only way they can determine it has evaporated, when
lab testing. So when we cool a hard drive, it's a simple
matter of physics, and trying to prevent the oil from
wanting to leave the spindle motor prematurely. You would
think it would make sense to have a rather large oil
tank connected to the motor, but it doesn't work that way

No problem, I'll just open my hard drive, and add a quart of 10w30
Pennzoil, I'll change the oil filter at the same time...... <LOL>

Seriously, can I just yank an old fan out of a dead power supply and
stick it on the back of the case? I got at least one dead ps laying
around? I hate buying stuff, when I got lots of junk around to salvage
from, not to mention I have to mailorder everything because there are no
computer or electronics stores nearby, and the shipping is usually twice
the item price, or more....

I needed a common electronics part the other day, the part was $1.79,
but the shipping was $9.99. (the thing weighs no more than 2 ounces,
and fits in any padded envelope). PLUS - there was a minimun $25 order.

I found the same $2 item on ebay from a private individual for $6, but
the shipping was included. I bought that one.....

Apparently the older computers did not need all that cooling. My Win98
machine P3 1000mhz has not had the case closed in at least 10 years.
That's because the original cheap piece of shit 100W power supply died.
I replaced it with a 350W ps, that's nearly twice as big, so it sticks
about an inch above the case. Thus the cover wont fit. The harddrives
in that machine both just sit on top of the case. I've never mounted
them, because I used to change them too often to run other systems. I
probably could now mount them since I have other computers for testing,
but I doubt I will.

 

[casey.o]

| Above, I meant to add that all my fans shut down in S3 sleep. According
| to my UPS, I only draw 3-4 watts while snoozing. This means that the
| power supply is cooperating (actively or passively) since all fans, no
| matter their connection, are off.
|

That's odd. I used to have a rear fan plugged into
a standard 4-wire power socket coming from the
power supply and it kept running during standby.
I assumed that was the norm.

Just a thought, but if I have to buy a fan, I'd rather just buy a 120v
AC fan. wire it right to the power cord, and run it direct off the house
electricity. Why suck power from the power supply, which is needed to
run the computer itself, rather than waste it to run a fan. Not to
mention that the more power needed from the power supply, means the
power supply will run that much hotter. (which defeats the purpose).

And most OEM computer power supplies are rated too low in wattage
anyhow. If they are being stressed, I suspect that has a lot to do with
system crashes. People often tell me stories about Windows 98 crashing
and getting BSODs. I used to get that too. When the cheap OEM 100W
power supply fried in my old computer, I replaced it with a 350W. Since
then, I rarely have any windows crashes on Win98. In fact I cant
remember the last time W98 crashed (not including system lockups caused
by scripts causing my browsers to freeze, and make the whole system
hang, until I use CTRL - ALT - DEL and kill the browser. I actually
find Win98 more stable than XP.

 

[Paul]

No problem, I'll just open my hard drive, and add a quart of 10w30
Pennzoil, I'll change the oil filter at the same time...... <LOL>

Seriously, can I just yank an old fan out of a dead power supply and
stick it on the back of the case? I got at least one dead ps laying
around? I hate buying stuff, when I got lots of junk around to salvage
from, not to mention I have to mailorder everything because there are no
computer or electronics stores nearby, and the shipping is usually twice
the item price, or more....

I needed a common electronics part the other day, the part was $1.79,
but the shipping was $9.99. (the thing weighs no more than 2 ounces,
and fits in any padded envelope). PLUS - there was a minimun $25 order.

I found the same $2 item on ebay from a private individual for $6, but
the shipping was included. I bought that one.....

Apparently the older computers did not need all that cooling. My Win98
machine P3 1000mhz has not had the case closed in at least 10 years.
That's because the original cheap piece of shit 100W power supply died.
I replaced it with a 350W ps, that's nearly twice as big, so it sticks
about an inch above the case. Thus the cover wont fit. The harddrives
in that machine both just sit on top of the case. I've never mounted
them, because I used to change them too often to run other systems. I
probably could now mount them since I have other computers for testing,
but I doubt I will.

As long as it's a 12V fan, and has a standard connector pinout,
knock yourself out

The one I replaced, seemed to meet that description, but read the
label on the fan hub, for hints if it's not standard. (There are
no "user replaceable" parts inside a PSU, so they can use any old
fan they feel like.)

Check your motherboard downloadable PDF manual, for the
fan header pinout. Compare to the wire colors on the cable.
Black is GND (ground). Red is usually a positive voltage, like 12V.
An optional third wire is the tacho output, which is not present on
a lot of cheap fans. I think all my case cooling fans, lack
the third wire.

Just try to make sure the power wires on the fan, get connected
to matching power connections on the fan header. So nothing
gets blown. Motherboards have no fuse in the fan power path!

Paul

 

[Mayayana]

| > That's odd. I used to have a rear fan plugged into
| > a standard 4-wire power socket coming from the
| > power supply and it kept running during standby.
| > I assumed that was the norm.
| >
| >
| Monitor off, fans spinning, is S1.
|
| Monitor off, fans off, is S3/S4/S5.
|

According to this....

https://en.wikipedia.org/wiki/Advanced_Configuration_and_Power_Interface

..... standby is S3. Standby is the only option I see
in the shutdown window. It puts my PC on standby,
with fans and disks off. The loaded OS remains in RAM.
But when I had a rear fan plugged into a power supply
cord it did not turn off in standby. That was a recent
power supply, maybe 3 years old.

I don't understand how these levels fit in. There's
only one standby. One can choose how the PC wakes
from it via hardware, but I don't know of any other
options. I also don't see any related settings in my
BIOS. Am I missing something? Are you saying that
you're somehow able to adjust standby to be a number
of different states?

 

[Mayayana]

| Just a thought, but if I have to buy a fan, I'd rather just buy a 120v
| AC fan. wire it right to the power cord, and run it direct off the house
| electricity. Why suck power from the power supply, which is needed to
| run the computer itself, rather than waste it to run a fan. Not to
| mention that the more power needed from the power supply, means the
| power supply will run that much hotter. (which defeats the purpose).
|
| And most OEM computer power supplies are rated too low in wattage
| anyhow.

I did that once, with an eMachines. I think the power
supply was something like 240 watts and I had two
hard disks in it. So I got a nice fan at Radio Shack, wired
it up, and just plugged it in when the computer was on.

 

[Paul]

| > That's odd. I used to have a rear fan plugged into
| > a standard 4-wire power socket coming from the
| > power supply and it kept running during standby.
| > I assumed that was the norm.
| >
| >
| Monitor off, fans spinning, is S1.
|
| Monitor off, fans off, is S3/S4/S5.
|

According to this....

https://en.wikipedia.org/wiki/Advanced_Configuration_and_Power_Interface

.... standby is S3. Standby is the only option I see
in the shutdown window. It puts my PC on standby,
with fans and disks off. The loaded OS remains in RAM.
But when I had a rear fan plugged into a power supply
cord it did not turn off in standby. That was a recent
power supply, maybe 3 years old.

I don't understand how these levels fit in. There's
only one standby. One can choose how the PC wakes
from it via hardware, but I don't know of any other
options. I also don't see any related settings in my
BIOS. Am I missing something? Are you saying that
you're somehow able to adjust standby to be a number
of different states?

I used to have another article with the states explained.
This one will have to do as a substitute.

http://arstechnica.com/civis/viewtopic.php?t=354552

S0 The system is turned on. The CPU is executing or
ready to execute instructions, PCI activity is full,
AGP activity is full. RAM is being read from, written
to or refreshed. Hard disks are on.

S1 "Power On Suspend/Stopgrant" MS: Standby
The system is turned on. The CPU is not executing and
is not ready to execute instructions, although registers
and caches are maintained. Devices signalling support
for S1 are in the on state, devices without support for
S1 are in the off state. RAM is idle, but refreshed.
Any device currently in S1 with support for resuming
may resume the system (WOL, WOR, keyboard, mouse, timer, etc.)
PSU state is on. Hard disks are off in this state and
all states deeper.

S2 "Standby" Confusing "common" names. S2 is quite logically
an intermediate between S1 and S3. RAM refreshes normally.
The CPU is in state much like S3. In fact, this is pretty much S3
but with a faster RAM refresh. S2 is in the spec, but not
usually implemented.

S3 "Suspend to RAM" MS: Standby (if notified by BIOS)
S3 often needs enabling by jumper on the motherboard or by
support in BIOS. The CPU is not executing instructions, is not
ready to execute instructions, does not maintain its registers and
does not maintain cache. The OS must flush dirty pages from the cache
when S3 is entered. Devices able to support S3 and are enabled for
resuming, may resume the system. PSU state is off, system RAM is
refreshed (at reduced refresh) using 5Vsb. External peripherals
(keyboard, mouse) may or may not be able to resume the system, depending
on what their host controller does.

S4 "Suspend to disk" MS: Hibernate
All hardware is in the off state and maintains no context. The
system may only be resumed by timer or other hardware resume devices
(such as WOL or WOR), but not by interrupts. The contents of RAM are
saved to disk and replaced on resume. The PSU is in the off state. Power
may be mechanically removed without ill effect.
Note: S4BIOS is a variation of S4 wherein the BIOS reloads the image and
not the OS boot loader. As NTLDR is S4 compatible, this is generally used
with other OS'. Linux S4BIOS support is "experimental". Note also that
using Windows2000 or XP with grub or lilo WILL break S4 support.

S5 "Soft-Off" MS: Hibernate
All hardware is in the off state and maintains no context. CMOS is
maintained by 5Vsb, as in S4. The PSU is in off state. Power may be
mechanically removed without ill effect.

*******

The part I might dispute about S1, is I thought the disks continue spinning.
I thought the idea was only to save monitor power, but otherwise leave
the PC ready to do stuff at a moment's notice.

S2 typically isn't implemented. This can be seen when reviewing
the output of dumppo.exe.

Users typically end up with the S1 flavor of standby, after
the BIOS is misconfigured (sometimes after a CMOS reset), the OS
is told S3 is not supported, and it reverts to S1. Using dumppo,
you can do an adminstrative override, to return S3 capability to the
system. You start by verifying the BIOS has S3 enabled. Then boot
the OS and use dumppo.exe from ftp.microsoft.com .

ftp://ftp.microsoft.com/products/Oemtest/v1.1/WOSTest/Tools/Acpi/dumppo.exe

http://forums.pcper.com/showthread.php?p=1825058&postcount=31

If the results looked like this:

dumppo.exe admin cap

Min sleep state......: S3
Max sleep state......: S4
System states supported.: S1 S3 S4 S5

it would likely be impossible to go into S1. That's because
the min sleep state is S3. And S1 can't be accessed by a
request to sleep.

Paul

 

[Paul]

| Just a thought, but if I have to buy a fan, I'd rather just buy a 120v
| AC fan. wire it right to the power cord, and run it direct off the house
| electricity. Why suck power from the power supply, which is needed to
| run the computer itself, rather than waste it to run a fan. Not to
| mention that the more power needed from the power supply, means the
| power supply will run that much hotter. (which defeats the purpose).
|
| And most OEM computer power supplies are rated too low in wattage
| anyhow.

I did that once, with an eMachines. I think the power
supply was something like 240 watts and I had two
hard disks in it. So I got a nice fan at Radio Shack, wired
it up, and just plugged it in when the computer was on.

I hope you meant " when the computer was *off* " there
in your last sentence.

It's not a good idea to take chances with the three pin
or four pin fan headers. They don't even have fuse protection,
and making a mistake with the power on, spells "smoke". If you
short the +12V on the fan header, to ground, it'll burn out
the fan track. And then none of the fans will work from their
headers, and you'll need to rewire the fans to run directly off
a power supply Molex. (The fan track is typically rated for
around 2 to 3 amps or so - the designer of the motherboard,
selects a copper track size so the track will burn out if
anything nasty happens.)

All it would take, is bending the +12V pin until it
touches the GND pin, and then the fun begins.

There is yet another reason not to connect a fan "hot".
I did that once, and the transient caused the computer to reset!
Do it with the computer power off. This is the real reason I
no longer even think about doing this. I might have been
tempted, but what's the point if there is a risk the
computer will be rebooted. Might as well just shut it down properly
and add a fan. That'll save having to run CHKDSK later.

Paul

 

[Mayayana]

| I used to have another article with the states explained.
| This one will have to do as a substitute.
|
| http://arstechnica.com/civis/viewtopic.php?t=354552
|

This is more complex than I realized. Though S1 and S3
don't seem to be very different. If I call up the
shutdown window I have a choice between standy,
shut down and restart (assuming I haven't enabled
hibernate). That standby is what I'm referring to as
standby. (I've never seen anything else called standby.
The option to turn off monitor or disks after a period of
no use is referred to as a "power scheme" in the Power
Options applet. Maybe that's S1?)
In my experience standby has always been the same
thing on any machine: The system shuts down, the
power light flashes, the RAM content is maintained. BUT,
fans plugged directly into a power supply socket keep
running. I wouldn't think something like conserving
CPU cache would affect that.

| Users typically end up with the S1 flavor of standby, after
| the BIOS is misconfigured (sometimes after a CMOS reset), the OS
| is told S3 is not supported, and it reverts to S1. Using dumppo,
| you can do an adminstrative override, to return S3 capability to the
| system. You start by verifying the BIOS has S3 enabled. Then boot
| the OS and use dumppo.exe from ftp.microsoft.com .
|
|
ftp://ftp.microsoft.com/products/Oemtest/v1.1/WOSTest/Tools/Acpi/dumppo.exe
|
| http://forums.pcper.com/showthread.php?p=1825058&postcount=31
|

This is an interesting topic I was completely
unaware of. The MS link doesn't seem to work,
but I found this recommended in a sysinternals forum:

http://www.bellamyjc.org/fr/windows2000.html#veille

There's a download there. I ran it and got the following:

c:\windows\desktop\dumppo.exe admin cap
Min sleep state......: S1
Max sleep state......: S4 - hibernate
Min video timeout....: 0
Max video timeout....: -1
Min spindown timeout.: 0
Max spindown timeout.: -1
power capabilities
System power capabilities
Power Button Present....: TRUE
Sleep Button Present....: FALSE
Lid Present.............: FALSE
System states supported.: S3 S4 S5

That seems to be ambiguous. But it reset to min. level
3 without problem. I don't see any settings in my 3/2013
BIOS. I don't even see an "Enable ACPI" option.

I'm curious how dumppo works. It must be just applying
some sort of API call and/or Registry setting.

I don't have my older PC running -- the one with the
fan that runs all the time. If I get it running I'll have to
try dumppo to see if it stops the "hotwired" fan running
during standy. (I haven't put a rear fan into my latest
machine. The reason for that is partly the running-during-
standy problem, but also because CPUs are much improved
these days. With the ability to shut off for micro intervals
while running, I find that even in a heat wave, the AMD CPUs
I buy generally only run a bit higher than room temperature.)




| If the results looked like this:
|
| dumppo.exe admin cap
|
| Min sleep state......: S3
| Max sleep state......: S4
| System states supported.: S1 S3 S4 S5
|
| it would likely be impossible to go into S1. That's because
| the min sleep state is S3. And S1 can't be accessed by a
| request to sleep.
|
| Paul