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To big for it. Since I'm thinking that, I want something that's going to be silent (fanless maybe) and very efficient as I don't plan on adding extra fans because I want a silent or near to it setup with decent performance. On that note I have also considered going with the 700 mhz Bananias Pentium M due to the Ultra Low Wattage of it (-4 watts I think).Negative 4 watts? That is ultra low!!!fastturtle wrote:On that note I have also considered going with the 700 mhz Bananias Pentium M due to the Ultra Low Wattage of it (-4 watts I think).
I understand exactly what you want. But you apparently don’t understand how PSU's work.fastturtle wrote:m0002a: I guess you didn't understand my concern: the existing PSU is TO BIG so what I need to do is downsize to something smaller.
Where's this 45% minimum load requirement from?fastturtle wrote:that's a total maximum draw of 130 watts. Well below the 45% minimum load for a Seasonic S12-330.
There are DC/DC PSUs with 200W capacity. Such could be ideal for you.fastturtle wrote:that's a total maximum draw of 130 watts.
- CPU 15 watts
- Burner 30 watts
- Hard drive 25 watts
- Motherboard 25 watts
- Geforce2 MX400 25 watts
- Sound Blaster PCI sound Card 10 watts
Don't even mention a DC/DC PSU such as the mini-itx can use. This system isn't quite that low power, although I guess it wouldn't take much to get it down below 100 watts.
Your CPU draws= 20 wattslm wrote: Oh and my server is quite similar to your system, and it only draws 40W on idle, 60W max. (measured with a power meter plugged between the wall socket and the psu power cord) Specs:
P3 733MHz slot1
512MB 133MHz sdram
80GB seagate barracuda IV pata
matrox millennium 1 (1997)
intel mobo with integrated sound
2* intel 100Mbps nic
4* papst 80mm fan @ 5V
If such a minimum load requirement did exist for PSU's, then most of the custom built PC's in the world would be unstable (which they are not).lm wrote:As I never heard about 45% minimum load stability limit before, I'm using sth like a 250W-350W PSU but I don't really remember and opening the case is too hard after what I've done to it. In any case my system is very stable, and I've achieved uptimes of over half a year, only went down because of power outage or kernel upgrade. So I think it's safe to say my PSU doesn't have such stability limit, or it's way lower than 45%.
I think I've figured it out. LM Thanks for the info on that DC/DC PSU. What I'm going to do, is build a custom setup using a battery charger to keep a pair of 12 volt Gell Cells topped off and run the system using the DC/DC PSU from those 12 volt batteries. Consider it as installing a UPS right in the case.I've never even considered getting a UPS, so I don't know much about it, but I think I've heard that active PFC makes a huge difference with UPS's.fastturtle wrote: In my case, it's simply the desire to build not only a silent system but one that's as efficient as possible. Every little bit helps especially when the #&^%$ powrer goes out and I'm on the UPS once again, so a correctly sized PSU is going to extend the battery life of my UPS due to efficiency.
It does seem like a much better idea to have the UPS placed after the AC-DC conversion, but are you sure that the batteries will give stable enough power or the DC-DC PSU will regulate it well enough?fastturtle wrote:
Your claim that PSU's are unstable unless using 45% of the load is ridiculous and there is no documentation of such a phenomenon, and not even any serious anecdotal reports. If you Windows OS crashes frequently, you have other problems. My Windows 2000 or XP has only blue-screened two or three times in the last 5 years, and both times caused by an application problem.fastturtle wrote:As to the 45% stability limit, how many people could tell if that windows crash was related to the PSU or software? I sure as hell couldn't tell you myself without having a hardware voltage monitor hooked to all rails constantly outputing to dedicated storage and without that, not even a good engineer could tell for sure unless he knew the PSU was oversized.
Fact is that I rarely see anyone else asking about the PSU unless they've indicated a major upgrade recently. Most times it's "is my video card going bad?" or My system is very slow, what can I do? To many people don't understand or even think about how much power they're system needs for stability and they're not aware that it's possible to have too much power and not run the PSU efficiently and that can cause as much problem as to much load for the system simply because unlike an underpowered car climbing a steep hill in the fast lane, you aint aware of it.
In my case, it's simply the desire to build not only a silent system but one that's as efficient as possible. Every little bit helps especially when the #&^%$ powrer goes out and I'm on the UPS once again, so a correctly sized PSU is going to extend the battery life of my UPS due to efficiency.
How did you come to the above conclusion? Where is the source for this claim?fastturtle wrote:Most ATX PSU's are designed with a minimum demand load for stability. This seems to be between 42-48 percent of designed maximum output.
That's 7.7W, which is less than 3% of a 300W PSU.fastturtle wrote:Here's the voltage regulation per rail from the same link:
±5% ±5% ±5% ±5% ±5% ±5%
With such a allowable swing in voltage regulation, I'd have to wonder just how stable this thing is going to be at minimum loads but these figures are actually pretty standard of most PSU's. What makes the difference is the listing of the minimum load current on each rail. I'm assuming that means the least it can provide.
Again from their Chart:
0.3A 0.4A 0.4A 0.3A 0A 0A
So if the PSU will not run unless it's putting at at least .9w on the 3.3 and 2w on the 5 and 4.8w on the 12 volt rails, I'd almost have to say that I've now been proven. What you will not find is the actuall specification for a 45% minimum load. This figure may and does vary and is never published.
Yes, sometimes this happens. Often it doesn't. I don't think it happens enough to say that a power supply isn't stable throughout most of its range.fastturtle wrote:Qestion: What happens when you upgrade a system to higher performance components but keep a weak PSU?
Answer: You end up with an unstable system.
This is just wrong. If anything it would overvolt the motherboard, not overclock the CPU. But, the reality is that it will do neither. The extra voltage will simply be absorbed by the PSU circuitry on the motherboard, which steps down the voltage even further before they're fed to the CPU chip. Yes, out of spec PSU voltages can lead to variances in the voltage fed to the CPU, but keep in mind that most CPUs can tolerate a voltage range of almost half a volt. That's about +/-30%, assuming a nominal voltage of 1.5V. People have had systems stable down to below 1V (after unclocking as well), and, although I'm less knowledgable about overvolting, people do frequently add 0.1V in order to improve stability at higher speeds.fastturtle wrote:Question: What happens when you o'clock a system w/o thought?
Answer: You end up with an unstable rig and that's what happens with a PSU that's oversized. It basically o'clocks the rig w/o you even being aware of it due to the voltages being high.
What we have here is what Plato called the difference between a true opinion and knowledge.fastturtle wrote:Remember that a Rule of thumb is just that. It's not carved in stone. Instead it's a generally accepted design practice. Good example is Doorways. Why don't we build our houses with Round Doors as hobits do?Rule of Thumb.
Everyone seems to disbelieve the 45% stablity loading of a PSU:
Here's the explanation as I understand it - Note that I am not an engineer so some of it could be wrong.
First of all, I didn't post that link. Where did you get the 20w figure? I get about 12w from the Antech specs (0.3A*5V+2*0.4A*12V+0.3A*3.3V). 12w is 3.5% of 350w. Not very close to your 45%...fastturtle wrote:Now according to your post, Antec states a Minimum of 20w load for this PSU.
Again, you just throw the figure with no data to show where you derived it from.fastturtle wrote:This factor is generally 45% of the maximum design load for cost efficiency.
PFC has nothing to do with output filtering. PFC tries to keep input AC voltage and current at the same phase thus maximizing the power factor (real power/apparent power).fastturtle wrote:Originaly PSU's didn't include active/passive PFC, That's only come around in the last 3 years. So originally PSU's had stability issues due to the simple fact that they weren't designed to filter their output.
Actually, ATX standard does specify basically (expect -12V rail) the above margins for voltage regulation. In addition, +12V rail can go from 10.8V to 13.2V during peaks. Yep, that is a 2.4V range. Check http://www.formfactors.orgfastturtle wrote:I will have to check the ATX specs for allowable voltage fluctuation but when you have a quality PSU that according to the Link provided by paapaa:
Here's the voltage regulation per rail from the same link:
±5% ±5% ±5% ±5% ±5% ±5%
Actually it just tells that Antec guarantees the PSU to give the performace described if the minimum conditions are met. It does NOT mean that the PSU "will not run" if less load is used. And no, you have not shown anything that proves the 45% figure. Again, the above equals to 12w load.fastturtle wrote: Again from their Chart:
0.3A 0.4A 0.4A 0.3A 0A 0A
So if the PSU will not run unless it's putting at at least .9w on the 3.3 and 2w on the 5 and 4.8w on the 12 volt rails, I'd almost have to say that I've now been proven.
All I can say is that your information is totally out-dated. Your are talking about AT or even pre-AT days!!!! There is no point in comparing 1985 AT supply to a modern ATX/BTX PSU. Please read this page:fastturtle wrote: What I saw happen was data corruption in memory that caused the system to crash. This was back in 1985 so it may not be as likely due to design improvement of the motherboard but why risk it when it's easily avoidable.
The regulation tolerances shouldn't have anything to do with oscillation. Oscillation happens, as you said, in higher frequencys. These stability requirements (stability has nothing to do with voltage regulation) is also covered in ATX design guide at Formfactors.fastturtle wrote:All PSU's oscilate around the core rail voltage. This is shown in the allowable variation/tollerence from standard of plus/minus 5%. What happens though is that the PSU's now have tighter voltage control so the oscilation is at a higher frequency, which could explain why the caps on some motherboards begin to whine/squeel.
You made the next claim which you can't prove:fastturtle wrote: All of the input has been apreciated, even the attempts to prove me wrong on some of my statements but No One ever proved that my 45% rule of thumb was invalid for the usage I made of it.
Umm, the problem here is that the 45% figure (or 42%-48%) is nonsense. I'm totally sure that all the ATX PSUs you'll ever use will function perfectly at 45% load. But they will also function perfectly at 20% load. Many if not all will function perfectly even at 5% (and in that case the PSU is oversized because of bad efficiency at low load levels) as Phantom 350w does, for example. The 45% figure has no practical meaning at all. A few examples from specs:fastturtle wrote:Most ATX PSU's are designed with a minimum demand load for stability. This seems to be between 42-48 percent of designed maximum output.
(I think this issue is now cleared)