Variations between PSU Calculators
So I've got my old 2010 system rebuilt for my wife to use and found my old PSU was shorting out so went to the cupboard and dug out an old 300 Watt unit that I had collecting dust. It is working fine. I had posted this in another thread. Old 300watt PSU I did take the advice and removed the video card and it's now running off the onboard video and is fine for word processing and surfing using that old PSU.
But now I've upgraded my video card to a HD 7970 I thought I check and see if my Antec 620m is still adequate for my main machine. And then I'd upgrade my primary system's PSU and retire the 620m to the back room PC.
The system used in this testing is my A10-5800K, HD 7970, 2 x Sata hard drives, 2 SSD's (not all ask for that) 1 blue ray, 2 USB powered devices, six case fans, two cpu fans.
What I found was a wide range of opinions from several PSU Calculators I brought up.
Entering the same data as much as possible (some asked more details like fan size, whether they are LED, etc other don't ask anything about fans) But in as much as I could I filled out the forms completely.
I thought maybe I'd buy a PSU powerful enough to allow for two HD 7970 in Xfire if I upgrade to that later.
Here is what I get told:
ASUS - 750w recommended. Xfired = 1150w
Xtreme - 437w min, 487w recommended, Xfired 583w min, 633w recommended
Coolermaster "recommended minimum" 438w, and Xfired = 601w
Thermaltake recommends 470w and 617 if Xfired.
Newegg.ca recommends 595w, Xfired = 920w
vbutils.com recommend precisely 449.9w and adds "I highly recommend Antec TruPower Power Supplies"
BeQuiet wants me to buy their 750w or 850w PSU
So four of the seven I checked recommend between 438-470, Newegg wants to sell me a slighter bigger one at 595w. And ASUS and Bequiet recommend 750w.
So what's up with this variation of about 50% more watts for those two over the others?
Based on who asked the most questions and the fact they considered things like overclocking I'm inclined to trust Xtreme and in as much as the others (except vbutils ASUS) are in the business of selling PSU's I'd expect them to recommend more watts. Not sure what to make of ASUS because best I can figure they don't sell PSU's - so why the 50% more watt's recommended than others? Extra margin of safety? But 50% more???
Which PSU Calculator do you trust?
And what about brands and features?
Antec has been recommended to me as the best more reliable PSU, and I've been told two or more 12v rails is a good thing (my current HCG has only a single rail).
I was tempted by a Fractal Design 750w because it was on sale fo $59 at NCIX.com but just because they make nice cases does that qualify them as a good PSU maker?
Wall of text..
PSU Calculators suck and are not worth using at all.
Get a Corsair 500w or 600w PSU and call it a day.
For a nice reliable long term build I would on 7970 I would say >600w (your 620 is fine) on a single or 850w for crossfire. PSU calculators are garbage. Go for antec, seasonic, corsair, or xfx and you will have a quality PSU.
Not that you need me to sound like a broken record here but don't use calculators. Period.\
When I had my i7 with SLI 460's and a few Black HDD's the calculators said I needed 850W min.
My HX650 did just fine. My APC never showed more than 400 from the wall.
Good Enough for Now
I guess there is no point in upgrading either of these PSU's as the 300w oldie is still working fine downstairs with the 2010 Athlon x4 system. I do have a pair of HD6670's in a box but maybe I should try selling them, and even the nVidia 9800xt.
The 620m seems to be handling the job just fine. If and when I add a second HD7970 I'll just have to factor in a new PSU into the cost of that upgrade.
Is there a way to see how much power is actually being used? In my research I see that Thermaltake promote a PSU monitoring system on their "smart" PSU's. Is there a utility or ?? where I can see just how many watts are being used at a particular moment?
The easiest way is a small power meter/monitor. Not perfectly accurate, but I got one at canadian tire for around $20... It plugs in an outlet then you plug the computer into it (has an LCD screen on it to show power use/peak power draw/etc.
Here is one available at CT now:
Hampton Energy Monitor | Canadian Tire
Mine was a different brand and it looked better, but this gives you an idea of what I am talking about. Like I said...they aren't going to be perfect, but it gives you a pretty good idea of the power you are pulling from the wall.
For gaming rigs, it's not wattage that matters, it's amperage on the 12v rail. Basically there is a ton of B.S. out there. This is why PSU calculators are useless. You're going to need 22.5 to 25 amps on the 12v rail per 7970. So that's 45-50 amps on the 12v rail to run xfire 7970 plus whatever else your system draws.
So a minimum for 7970x2 that I would recommend is a corsair ax 850. This should run 2 7970 overclocked and an overclocked system.
I always go overkill on my PSU selection so that it runs cool and quiet. So personally I would get a 1000 watt PSU for dual 7970, but that's overkill.
How unreliable PSU calculators are is/was one of the main reasons I wanted to essentially build my own interface between your hardware components and the psu to see what the actual loading was per item and allow a psu calculator to pull up that more accurate data.
Sadly it's been too expensive for me to attempt this right now even with some of the support I had gotten when I first started the project. The problem is it's not cost effective thing to produce and then sell, unless it was to enthusiasts who wouldn't mind spending 150$ on it (or at least pay for parts/labour)
Gonna get me one of these
Thanks for the education on PSU Calculators - it is confusing for the less informed to understand. IF and when I upgrade to a second HD7970 I'll be sure to get at least an 850w with plenty of amps per rail. I see that the larger wattage units tend to have more than one rail.
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