ronics Design magazine, maybe a Bob Pease
That helps confirm what I thought. The process of computing the power isn't complicated, it's simple. You just have to multiply voltage times current and do it fast enough that you are accurately sampling the waveform. It doesn't take a very complicated chip to do that. And we've had cheap consumer electronics for decades that does a lot more, eg calculators.
On Mon, 18 Mar 2013 06:15:34 -0700 (PDT), snipped-for-privacy@my-deja.com wrote in Re Re: OT: Computer power supplies and you guys being smarter than I...:
What is a "nonlinear" vs. "linear" type waveform, if you don't mind?
The terms may not be correct, but normal power follows a sine wave curve going from 0 volts to a plus voltage and back to 0. It then follows the same sine wave curve to a maximum negative voltage and back to 0. For what is often called 120 volts at 60 hz really has a peak voltage of around 170 volts. Most old analog meters were designed to 'average' this value to what is called a RMS value. Sometimes this has been the same voltage an equal voltage of DC would heat a resistive load.
Newer devices often take the power in pulses so it does not use the whole part of the sine wave curve, but just spikes of voltage or portions of the sine wave. It is often difficult to measuer this voltage/power with simple meters.
Good links. They push high watt PS's because they're more profitable. Kind of like a 500hp car that can go 180mph. But never does. Just a while ago I became aware of how much overpowered PS's are in an internet forum discussion. The guy who knew all about it caught hell. Somebody was doing a build and he recommended 400w. I thought that was low, and said so. He responded with facts and cites, so I reversed my position. He still caught hell from a bunch of others with overkill PS's. Some of it was his attitude. Wasn't shy being about being knowledgeable. Bottom line as add up peak component watt usage, and possible future additional watts, and buy quality at those watts. Most people have more wattage than they need, just like many have more hp than they need in their cars. There's an efficiency penalty, but with a PS it doesn't add up to much. I've got a 600w Corsair and a similar setup as the OP. I added a second GPU this year to get good PhysX in a game, and noted that by having the 600w PS I didn't give it a second thought. That was only reason for disagreeing with his lowball watt suggestion. He said 400w would have worked for me as well, so I really looked at all the numbers. He was right. But I don't regret having the 600w. It's overkill. Not a big deal. The 750w Corsair is overkill, but not a big deal unless you want to make it so.
Nothing wrong with an oversized power supply. Will likely last longer than a "right sized" or borderline supply. I almost always use
600 watt replacements - they generally cost me about $5 more than a 250.
build, and I'm using a kill-a-watt type meter to do so. Anyone know just h ow accurate these meters are when it comes to power supplies? Most power su pply sizing webpages imply that I'd be using 500-600 watts for my pc. I ass ume this is under 75 or 90% load or somesuch. Yet when I measure with a kil l-a-watt knockoff meter it's around 90-130 watts. Power supply in question is a corsair TX750. PC in question is an I7 3770K with 1 ssd, 9 sata harddr ives (all low RPM), 5 120mm fans, nVidia 650ti 1 gb vid card, 4 sticks of r am, 2 pci cards, a few usb 2 devices.
It's going to draw a lot more if you ut all those drives to work.
You don't mention the drive sizes but 9 is a lot. Why low speed? I'd go 7
200 or 10k myself for a media server. But the network is probably your bot tleneck anyway.
Great power supply. I have several of those running our machines. The actual wattage that the machine uses should always be less than the capacity of the supply. It's certainly not hurting anything or costing anything to have an oversized supply
Will be sticking with the supposed oversized PSU.
The Kill-a-Watt (and most meters) won't tell you what's important in this case, and that's how much *startup* current those 9 drives, etc. all draw when the machine is first turned on. I'll bet it's far higher than the running current. With that many drives it's probably always best to err on the side of caution and make sure you have enough power to start up the machines.
Just because it has a 500 or 700W rating, a huge switching PS doesn't consume significantly more power than a smaller one when running the same sized load. It just has the ability to run a *larger* load if need be and to handle startup current draw better. I've been able to see the startup draw of my refrigerator briefly on the Kill-a-Watt display and it's substantially higher than where the reading settles at once it's up and running. Maybe if you watch the Kill-a-Watt display as the computer starts up you'll see the difference between starting current and run current.
Some of the earlier drives, like full-height Seagate 40MB "desk shakers" had to be set up to "stagger start" when multiple drives were installed just to keep the PS from overloading during bootup.
That means that the drive won't spin up until the drive controller receives the appropriate request via a software or firmware command. Those were the good old days. (-:
I would guess that hard drive technology has improved to the point where your nine SATA drives don't draw as much current as that one huge 40MB Seagate, especially when starting up. Still, with that many drives, your PS has to be sized for the maximum startup current, which in a setup like yours is going to be quite high.
Gaming video cards are also notorious for requiring substantial power to start. So much so that most modern high-end video cards now have a direct connection to the PS instead of drawing power through the card bus.
As always, HomoGay, you haven't a clue what you're talking about.
(Electronics Design magazine, maybe a Bob Pease
Correct. There are some subtleties but that's basically it. Kill-A-Watts, and similar, are amazingly good at what they do for the price charged.
It only draws that much if you are using it for something that requires it to WORK hard. Surfing the net is just loafing for the video card and I may only be drawing 25 watts. A lot of time the manufactures specs will show the range. It's when you are playing video games and pushing it to high frame rates that make it draw lots of power.
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