Slashdot Mirror
Ask Slashdot: Reliable Powering of ATX Systems?
David Muir Sharnoff
writes in with this question:
"ATX power supplies don't supply power unless the motherboard says to
turn on. Many motherboards do not have a setting of: 'supply
power all the time.' This means that ATX systems
cannot safely be used a servers. Anyone know of
an ATX power supply that ignores signal? "
More appropriately: does anyone know of an ATX
motherboard/power supply/case combination where powering
is similar to AT systems?
home would not bootup after a powershutdown.
After some investigation I found that most
ATX mobo's have a setting in their bios to
powerup after a powercycle.
-aj-
I thought ATX was a PC case description (I see it in ads). Now it seems its a power supply and what does this have to do with being able to be a server? This proto nerd is confused.
I had a motherboard (DEC AlphaPC 164) that didn't produce the DC-OK (aka PC-ON)signal. This is pin 14 on the ATX motherboard connector. You can cut this wire (usually green colored) and the adjacent black (pin 15) wire above the connector and wire them together with a wire nut so that it is always on whenever the power cord is plugged in. Or connect these two wires to a new switch and replace the ATX style switch on your case with a standard AT-like switch (this is what I did). I bought the switch at radio Shack for under a dollar. Works great. The only thing the DC-OK wire does is tell the power supply to go from sleep state to full power state. It does this when the pin is grounded. The black wire #15 is one of those unneeded ground wires that can be redirected to this task. I was educated to this method by PC Power and Cooling (www.pcpowercool.com) which is probably the finest producer of power supplies out there. Good luck.
I hav a related question.
Is it possible to have the ATX power switch act
like an SGI power switch(I press the button, I
runs shutdown then turns off).
Likewise with reset. If I press reset, can I have it run 'reboot'? Can I even control what happens with the reset button?(I just unplugged the thing, since it does nothing good(safe))
WTX will replace ATX for server boxes. It appears to be a good spec to me.
WTX.ORG
The ATX specification can be found here:
.htm
http://www.teleport.com/~atx/spec/index
(Boy I hope this message get moderated up.
That would be keen.)
Not where I come from - where I come from it just means that those motherboards can't be safely used as servers.
If you get a decent motherboard which has the required power setting, why would you need to play silly buggers with the power supply unit?
I know for a fact that the ASUS P2BF has a "AC Power Fail Auto-Restart" BIOS option and the Intel Nightshade has a "Restore Power State" BIOS option that will turn the power on automatically if it was on when AC power was lost (i.e. power was not turned off via the front panel switch).
Send mail here if you want to reach me.
Posted by el_steevo:
From the power supply wires coming from the power supply in the case to the MOBO, short the green wire to ground. This will give you power all of the time.
This might be related to the Linux "use" at Lucas Digital that caused some discussion last week. Then again it might not and it just made me think of it.
;)
If I had a rack of Linux servers with ATX supplies (which, coincidentally, I do), and wanted to make sure they came back on when power was lost (doh, didn't think of that, what are you running a server without a UPS for anyway???), then I might use a spare 386 or 486 I've got kicking around to do it.
Its a piece of cake to wire a relay to a parallel port, there's schematics all over the place on the net to do it. Trim the power supply's "on" pins, wire them to the relay, and you could easy control the power of 8 systems from the parallel port with maybe $40 worth of hardware. Its not exactly what the question was asking, but it might be useful. Maybe Slashdot needs something like this for when the machine misbehaves.
Also useful in case of an errant init 0 instead of init 6...
Alternately, I think those Matrix Orbital displays with the keypad interface also have eight digital outputs on them, you could wire one of those to a serial port, and trigger the relays with those outputs. Running some monitoring software to put the status of the machines on the LCD, you've got a nifty monitoring/control system.
Virtually all of those will hard power off even if the system is hung if you hold the power switch down for five seconds...
Sometimes they don't make that clear in the manual though. Its a problem if you have Linux on them and don't know that, and don't compile the kernel to shut the system off on halt.
Here's what it will cost to run a computer all month for your electric bill at home if you pay $0.08 per kilowatt hour:
40 watts * 0.08 cents/1000watthour *24hours * 30 days
=$2.30
If you get the industrial rate at $0.02 per kilowatt hour, that will be about $0.58 per box.
UPS supplies seem to draw much more. They seem to have a type of saturation transformer where the iron core is intentionally saturated with excessive current to give a well regulated and safe voltage to your computer including isolating it from the mains.
This works with an Award BIOS. Press RESET and press Delete key to enter setup. Open the "Power Managmement Settings" menu. Set the "Power Button Override" to "Enable" Save and Exit.
Look for APM (advanced Power Management) support in the BIOS and Linux. Should be doable. I've never looked into it, but it's the basic principle. Most modern bioses support sleep mode, which is functionally idle-type mode. Of course, you'll want an EnergyStar-certified monitor. Most modern monitors are. This sort of information was really big around six years ago, with major manufactuers shipping low-power systems, such as the IBM EV1(?) which had an LCD monitor (a rarity at the time, and expensive). If you look through PC Magazine there should be some information about Green PC's around 92 or 93. Additionally, I believe there's some info on power managament at: ftp://sunsite.unc.edu/pub/Linux/docs/HOWTO/mini/Ba ttery-Powered
Particularly Sections 3.1-3.4 (which describes APM)
Also HDPARM, which can be used to reduce the spin rate on the Hard Drive to reduce the power used.
But the question is why? Aside from the good for the environment angle, there isn't a pressing need for it. A computer only draws about as much power as an light bulb (last spec I heard about PC power consumption). If you REALLY want to save power, shut off the system. Sleep mode draws ~2-4 watts afaik.
Hope this helps,
--I hate people when they're not polite -"Psycho Killer", Talking Heads
The only linear computer supplies I ever saw in surplus catalogs came from discontinued mainframes, not bankrupt PC manufacturers.
Linear power supplies take the current from the wall socket and run it through the primary winding of a transformer. The secondary winding (in vacuum tube days a voltage step up, current step down--for solid-state circuits a voltage step down, current step up) passes the same wattage (voltage times current, sort of--it's a little more complicated with alternating current than with direct current)--minus what gets lost, due to less than 100% efficiency, and turns into heat--to rectifiers which "re-route" the alternating cycles so that the current flows in the same direction instead of reversing 60 times per second. This makes it direct current, but now the voltage goes from zero up to whatever the peak is and then back down to zero 120 times per second, so various passive (and sometimes active) components are used to filter and regulate the voltage. If the incoming frequency is higher than 60 Hz then smaller, lighter (less expensive) transformers and passive filtering components can be used. This is the reason for 400 Hz generators on aircraft, to save weight and space, although, in the case of aircraft, not money. The higher frequency = smaller, lighter, cheaper components relationship is also taken advantage of in switching supplies where the alternating current from the wall socket goes straight to the rectifiers, is changed into pulsating direct current, filtered to "average out" the pulsations, and sent to transistors which turn on and off somewhere in the neighborhood of 20,000 to 40,000 times per second. This results in a "pulsed" direct current which can be stepped up or down in voltage with a transformer just as with alternating current, but at the much higher frequency a smaller, lighter, cheaper transformer can be used. In both cases (linear and switching)the transformer electrically isolates the power supply's output from the wall socket supplied input.
I see even classic Slashdot is now pretty much unusable on dial up anymore.
So, you should be able to hack it together to have that pin permanently grounded, so that the PS is always on. I haven't tried this; I think it should work fine, but don't blame me if your motherboard burns!
There's also more info on ATX at http://www.teleport.com/~atx/
One major problem that I have experienced wth ATX power supplies is that since the fan is mounted on a horizontal plane it seems to be more prone to wear and "chuffing."
ATX motherboards are great since they reduce ribbon cable clutter. However, if you must use ATX you should ALWAYS get a motherboard that has AT power supply connectors (most aftermarket boards do). You'll save at least $30 and be able to get higher-rated power supplies for less money. You also won't have the annoying power button problems.
Kris
Kriston J. Rehberg
http://kriston.net/
Kriston
For all intensive purposes, an ATX motherboard and power-supply combo can "power-off" a system. This "feature" can be set up (usually) by using a combination of the BIOS settings, and the operating system.
However, there will always be a small amount of electricity flowing through the components from the power supply when it is off. With that in mind, the power supply is never fully, completely off. This is why it is best to unplug the power cord from a system before any tinkering inside of it is done.
Its not worth it. Most if not all cases come with power supplies. Also, replacement power supplies are relatively inexpensive.
Finally, the old power supplies were/are very inefficient; they work by using transformers to step down the voltage. The newer power supplies, including the ATX supply, are switching power supplies. This means that more of the power actually gets to the motherboard and less is wasted in the conversion.
-- Error: Cannot find file REALITY.SYS - Universe halted, please reboot!
ATX has a cleaner, more logical, less crammed design than AT. The changes (at least, the ones that spring to me now) are: :)
- The CPU is at the top, not in front of the cards. Many (most? [all?]) current processors will discourage you from using full-size cards on an AT motherboard because they are just in the middle.
- RAM is in a much more convenient place than just under the power supply, it is actually possible to fill your motherboard with RAM without unmounting the power supply
- Printer, serial, keyboard, mouse, USB, video (optional) and audio (optional) ports are soldered on the motherboard, so you won't have 5 extra cables on your case, which makes up a cleaner design, easier access and maintenance.
- IDE, SCSI and floppy ports are located actually near the disks, so your cables won't run all across the place - once again, cleaner.
- The boxes are a bit wider. I don't know what is that for.
- The fan on the power supply doesn't suck the hot air from the case, it blows fresh air in instead. What's the effect? I don't know.
- ATX motherboards can implement wake up on ring, LAN activity, keyboard activity or port activity, they are continously powered - I don't know if this can damage your computer in the long run. To keep safe, if you plan not to turn on the PC, turn off the UPS or regulator.
I tend to prefer AT because it has been the standard for many years and still works very good, and I don't think most people will need this features. However, I just bought an ATX systems (they were out of AT motherboards and I needed the machine immediately), and assembling it was much easier. Also, it's easier to spot a misconnected cable. I think I will start recomending ATX now.
At hardware and auto parts stores you can get solderless connectors which tap a wire into an existing wire. You can use two of them to add a wire which connects the wires for pin 14 and a neighboring wire. They're usually blue plastic with a metal tab which you push into the two wires. Faster than soldering and can be removed for maintenance.
An AT-style power supply connector usually cannot be installed "backwards" in that the connector is rotated 180 degrees, but "backwards" in the sense that the two connectors are swapped. Simple rule for AT power supplies: "Black to Black" - the five or so black ground wires should always be in the center of the two plugs.
Enjoy your job, make lots of money, work within the law. Choose any two.
Because the power switch goes through the MB instead of to the power supply it makes it more difficult to narrow down problems with a computer. Is it the Power Supply? Is it the Motherboard? You can't tell without popping out the power supply and trying a known good one.
Additionally, is it just me or are the ATX power supplies more fragile than AT's? I've had to replace two of them myself in the period of one year, and my brother had to replace his a few months after he got his. I don't know about him, but I have a UPS (APC) so I know my power is clean. And I've been buying good quality power supplies. Argghh, I like the ATX case design thing-ma-bobs, but I REALLY don't like the power supplies. Is it just me? Am I cursed? Or have other's experienced my travails?
BTW, this is very recent so it's not because I'm using pre 2.01 compliant power supplies.
There're a couple of options
Some ABIT motherboards can be strapped with a
jumper between the reset and power switch connectors to make them act in an 'always on'
fashion like AT motherboards do.
If you feel like experimenting a bit, you can
look in electronics parts catalogs for POST
transistors... these basically act like delayed
momentary-on relays. One lead goes to +5V,
the others go to the power-switch jumper.
--Z
It isn't possible to power an ATX motherboard with an AT power supply. The ATX power supplies produce an additional 3.2 volt output not present on a standard AT power supply. That is why modern motherboards that work with AT power supplies always have a big heatsinked part on them, to regulate and produce the lower voltage not availabe from an AT power supply (which only supplies +-5 and +-12 volts). A cord adaptor to allow you to use an AT supply on an ATX motherboard would have to incorporate a pretty fancy inline DC-DC converter to give the MB the voltages/current it needs.
Reset is a pretty cruel and unforgiving beast.
I suspect that a power-switch event could be linked to trigger a shutdown somehow, maybe in the inittable (?) like control-alt-delete is. It seems like pretty low-level hardware stuff, though. Does anybody know if power-switch handling is part of the ATX specification (which I believe is available at Intel somewhere) to make it worth the effort of something like this? (it would be a nightmare to have it be architecture dependent with tons of variations)
What kind of software do you use to make your server page you when it is about to go down?
:o)
Try
Big Brother... it works wonderfully for this.. (assuming your UPSd logs things like that
--bdj
Some of the comments I've seen hit it on the head: The Brand + Model + Revision of Motherboard you buy is key for ANY system (esp. a server).
/. you can usually tell which are which)
:) ) You'll want to make sure the PS is compliant with ATX 2.01 to be on the safe side too.
:(
Myself I don't like buying anything I haven't researched to death; I also really want to hear what other people's experience has been with the stuff. (note: people I trust... not some script kiddie; though on
Checking Tom's Site and Ars Techina to see what they think doesn't hurt either.
As far the Power-Always-On feature you want well, 3 things:
1) I would not recommend any soldering at all as your warranty will most likely go out the window. This can be a very bad thing in a corporate environment.
2) Most high quality Motherboards come with either a CMOS or Jumper setting (or combo) which tells the PS what to do when power is applied.
3) A good case goes a long way... both in ensuring you have a quality PS, and that you won't slice your fingers when you need to work on it. (Can we have a poll on how many times we've done that?
As far as personal choices, I'm a big fan of both Supermicro Motherboards and Cases - my personal fav is the SC-701a style case - it's a beauty! but unfortunately its soon to be discontinued...
Anyway, just my $0.02 (which is worth even less as its Canadian...)
I used to have a cool sig.
I have a Supermicro P6GDE (Dual PII 400, GX chipset) that has a jumper on the MB to choose, "Bios Power Stater, or Always on..."
As soon as I through the switch on the back of the powersupply its on, and if that switch is left in the on position then it comes on when the power returns after a black out, etc.
Note the case is a supermicro ATX750 or something(which is really an Antec Case and Powersupply) and it seems to be designed just for this...
VANBO
A while back, I did some current measurements on my ATX PC. Here are the results:
The eye-opener is the fact that, even with everything "off", the system is still eating 12 or so watts. I was expecting maybe 8W, but not 12W. ATX systems can eat significant power, even when off.
Note that the "full on" current was measured just after Win98 had finished booting. A CPU-intensive program like Quake or Unreal wasn't running. It would be interesting to see how much of a difference, if any, there would be.
It's also interesting to note that, if I disconnect all cables from the power strip and then measure the current, the power strip is drawing 0.01A (1.2W). This is probably leakage current from the surge suppression in the power strip (or measurement error in the ammeter).
These numbers are probably on the high side, as my system has a Voodoo 2 and two hard disks. Detailed specs:
Side note: from measuring my girlfriend's PC, which is virtually identical to mine except she has only one IBM hard disk and no Voodoo2 card, the Voodoo2 card and extra hard disk use up 0.27A or 32.4W. Most of this is probably from the Voodoo2 card.
Initial note on credibility: I have been in the employ of the leading manufacturer of power supplies for more than a decade, in a highly technical role.
Your conclusions are accurate, but your actual data is wrong. The power is way too high to be wasting on every PC on the planet, but is in fact significantly lower than you measured. The power into a PC power supply cannot be estimated by measuring the AC current and multiplying times the known AC voltage. This would work with in-phase sine waves or DC, but not with the highly distorted current waveform present at the input of the power supply. Most of the measured current is in odd harmonics (3rd, 5th etc.) of the 60 Hz line. Multiplying a 180 hz current times a 60 Hz voltage will give alternating positive and negative power over time, with zero net power. (i.e. the 180 Hz power alternately flows from mains to computer, then from computer to mains). Your current meter measures this as part of the total current, though it doesn't reflect power. (Your local Utiliy's Wattmeter is not fooled - it reflects true power).
A Wattmeter is required, and the error can be 3x. (Actual power dissipated is lower is lower than you calculate.) This has been a real pain for a non obvious reason. Typically, we design equipment for use on a 10A service (assumed minimum size of fuse/circuit breaker; the ratings on wiring, wall sockets, etc.), which would imply that we could go up to 1200 W without problem even in a consumer environment. In fact, we will exceed 10A RMS on significantly lower power units. High power systems (750W and above) will almost always need an additional power stage, a Power Factor Correction (PFC) front end, which pulls power from the mains in a clean sinusoidal waveform to allow us to extract the maximum power at a given RMS current level.
Two upcoming related issues will increase the cost of power supplies: In Europe, there is already a new requirement on the books that will require that the level of harmonics in the current draw be reduces (same as saying that we will be required to make the input current look more sinusoidal). This will be a new requirement on low power (consumer sort of power level) equipment. Second, the "low power" energy savings modes will be made significantly more stringent, which will have significant impact not only on computers, but on all that consemer gear that stays alive waiting for your IR remote to tell it to power up. Even little wall-warts will be affected. the power drawn by old fashioned steel transformer based warts is on the order of a Watt or two - multiply that number times the number of cell phone chargers hanging off people's wall sockets 24 hours a day and you'll see staggering costs to society.
whatever is - the music is