power supply question(s)

[adomas32]

i've done as much research as i could before coming to you guys. im building a new system
e6600, p5w dh, 7900gt KO blah blah blah. using outervisions psu calculator, i ended up with 415 watts. (this includes a 3000 mhz overclock at stock voltage) now, i looked at the newegg page for the 7900gt ko and under requirements it demands a 12V @ 20 A.

up until that point, i was planning to get the Forton FSP
http://www.newegg.com/Product/Product.asp?Item=N82E16817104954

but it looks like it only dishes out 18A per 12V rail. is this really a problem? if so, what would you guys recommend (450W under $60), or is that price too low?

 

[Arcanedeath]

For the system you listed that Powersupply will be fine it won't have that much headroom but it will still work just fine.

 

[Baked]

Another case of the buy high price components but skimp on the PSU. Here's what you should do. Get the E6400 instead of the E6600, and spend the money saved on a better PSU. Something from Enhance, Seasonic, OCZ.

 

[adomas32]

Minimum of a 400 Watt power supply.
(Minimum recommended power supply with +12 Volt current rating of 20 Amp Amps.)

when they say this, are they assuming that one 12 rail is going solely to the gpu? better yet, is it worth waiting until the dx 10 cards come out?

 

[orangat]

Adomas, the AX models including the one you linked is not good. Get the FX or FSP models of Fortron.

 

[SparkyJJO]

Originally posted by: orangat
Adomas, the AX models including the one you linked is not good. Get the FX or FSP models of Fortron.

what is wrong with the AX model I was told fortrons in general were good so a computer I built for someone I used that exact same PSU in.

darnit I thought I finally had the "good PSU" list finished and now there are stipulations to be put in.... :frown:

 

[promoter2007]

I am sure that for this system the ps is ok and will work fine!

 

[Howard]

Originally posted by: SparkyJJO

Originally posted by: orangat
Adomas, the AX models including the one you linked is not good. Get the FX or FSP models of Fortron.

what is wrong with the AX model

Bad caps, for one.

 

[SparkyJJO]

Originally posted by: Howard

Originally posted by: SparkyJJO

Originally posted by: orangat
Adomas, the AX models including the one you linked is not good. Get the FX or FSP models of Fortron.

what is wrong with the AX model

Bad caps, for one.

same or worse than antec (because I'm running an antec PSU)?

 

[adomas32]

ok, so the ax is no good. however, all the fx and fsp are 550 W and above. i really dont need more than 450 or 480.

 

[Howard]

Originally posted by: SparkyJJO

Originally posted by: Howard

Originally posted by: SparkyJJO

Originally posted by: orangat
Adomas, the AX models including the one you linked is not good. Get the FX or FSP models of Fortron.

what is wrong with the AX model

Bad caps, for one.

same or worse than antec (because I'm running an antec PSU)?

The same.

 

[SparkyJJO]

OK so at least I didn't give the friend a worse PSU than mine could possibly end up. So far so good, running fine but I'm a little nervous about it going bad on me. No $$$$ to replace it with though so I gotta keep it and hope it doesn't fail on me.

 

[Icepick]

Originally posted by: adomas32
i've done as much research as i could before coming to you guys. im building a new system
e6600, p5w dh, 7900gt KO blah blah blah. using outervisions psu calculator, i ended up with 415 watts. (this includes a 3000 mhz overclock at stock voltage) now, i looked at the newegg page for the 7900gt ko and under requirements it demands a 12V @ 20 A.

up until that point, i was planning to get the Forton FSP
http://www.newegg.com/Product/Product.asp?Item=N82E16817104954

but it looks like it only dishes out 18A per 12V rail. is this really a problem? if so, what would you guys recommend (450W under $60), or is that price too low?

18A per 12V rail means that the power supply is capable of delivering 36A total. When looking at multiple rail power supplies just add the total current output of all of the rails together. If you end up needing more than 18A on rail 1 due to the graphics card then it will draw the extra current and there will be less available on rail2.

Two rails rated at 18A (36A total current output) more than satisfies nVidia's recommendation and it will be more than enough for that system.

 

[acegazda]

Originally posted by: Baked
Another case of the buy high price components but skimp on the PSU. Here's what you should do. Get the E6400 instead of the E6600, and spend the money saved on a better PSU. Something from Enhance, Seasonic, OCZ.

Love the suggestions (though you linked a 400w, 500w and 600w... pick one!) all qaulity psu's. I would suggest the enhance unit, becasue you just don't need 600w for one video card. The MoBo might support xfire, but you got an nvidia card so that won't happen. The enhance has a combined ampage of 28amps, which should be fine even if you upgrade the card to a dx10 card in the [near?] future. It is also 80+ certified, which garentees that it has 80% or higher efficiancy, and it will generate less heat and noise. Check out jonnyguru's review of the unit here.

 

[dBTelos]

430W S12, 400W Enhance ENP, 400W Enermax Libert, 420W Vantec Stealth.

 

[imported_RedStar]

"18A per 12V rail means that the power supply is capable of delivering 36A total. When looking at multiple rail power supplies just add the total current output of all of the rails together. If you end up needing more than 18A on rail 1 due to the graphics card then it will draw the extra current and there will be less available on rail2.
"

i made this same mistake. It is not true. Read this:

http://www.extremetech.com/article2/0,1558,1932947,00.asp


and then read this for a better understanding of the complicated issue.


http://www.motherboards.org/articles/guides/1487_3.html


this is rehash from the thread in this forum:

http://forums.anandtech.com/messageview...&STARTPAGE=1&FTVAR_FORUMVIEWTMP=Linear

 

[acegazda]

thanx for pointing that out... seasonic is the only mfg that you can add up the amps on each rail and get the combined amps becasue they aren't LIARS! Anyhow, most mfgs put a combined wattage output under the two rails, then you divide that by 12 to get the combined amps... or you can email the mfg.

 

[imported_RedStar]

also use this tool for calculating PSU requirements

http://www.extreme.outervision.com/psucalculator.jsp

credit:
(link provided by Alisha in another thread)

 

[Howard]

Originally posted by: acegazda
thanx for pointing that out... seasonic is the only mfg that you can add up the amps on each rail and get the combined amps becasue they aren't LIARS! Anyhow, most mfgs put a combined wattage output under the two rails, then you divide that by 12 to get the combined amps... or you can email the mfg.

Claiming 20A per rail in a two-rail supply yet having only 36A combined isn't a lie, it's the truth. How else do you explain the fact that each individual rail can do 20A (if the max combined rating isn't hit) and yet they both cannot exceed 36A? Simple - say 20A for each with a combined rating of 36A. It's only deceiving when the combined max isn't listed.

 

[acegazda]

Yeah... srry, but the 400w version's combined is 30amps if I'm not mistaken. The 500w version is 36amps. I like the fact that seasonic makes it nice and easy though... oh and pcp&c doesn't make it confusing either, then again most of their psu's have only one rail anyway, so they better not lie!

 

[imported_RedStar]

also using the calculator i wondered over the psu utilization select option .

(read the first couple paragraphs of the review for this good PSU)

http://www.bjorn3d.com/read.php?cID=939

so basically you want the most watts you can get just so you won't tax your PSU (like 30% more than the required).

The numbers sure roll up fast. Yikes

It makes sense i guess...but is this overkill??

 

[Icepick]

Originally posted by: RedStar
"18A per 12V rail means that the power supply is capable of delivering 36A total. When looking at multiple rail power supplies just add the total current output of all of the rails together. If you end up needing more than 18A on rail 1 due to the graphics card then it will draw the extra current and there will be less available on rail2.
"

i made this same mistake. It is not true. Read this:

http://www.extremetech.com/article2/0,1558,1932947,00.asp


and then read this for a better understanding of the complicated issue.


http://www.motherboards.org/articles/guides/1487_3.html


this is rehash from the thread in this forum:

http://forums.anandtech.com/messageview...&STARTPAGE=1&FTVAR_FORUMVIEWTMP=Linear

These are informative articles. Thanks RedStar!

 

[acegazda]

better psu's with higher efficiancies need not take the 30% rule into equation becasue they deliver close to their promised power outputs.

 

[Howard]

Originally posted by: acegazda
better psu's with higher efficiancies need not take the 30% rule into equation becasue they deliver close to their promised power outputs.

Not necessarily. You can have low-efficiency PSUs that deliver what they claim. Zippy supplies, for example.

 

[imported_RedStar]

well..even the best efficiencies are only just over 80%.

edit: the point is ...as i understand it, If you use you calculator and determine that you need 700 w ...a 700w PSU is to be bought. But then that 700w has a power utilisation of 100%. An that is not good over time. So you buy a bigger PSU so it does not tax itself.

That's how i am reading this anyways.

edit:

Or, if you select 100% PSU utilisation..does that mean the calculator is already factoring in a cushion?

--
My own question is ...just how much power can you draw from a cicuit before your house explodes1? Heh, i want to go sli but the thought of 750W is scary (plus monitor, lights, printer, router and so on)