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power supply and the effect of amps ?

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June 3, 2006 3:56:48 AM

basically it comes down to this
I have a d805 and a7900gtx
currently with a ultra xfinity 600w psu but as might be known the d805 is power hungry and speed fan is showing my 12v line dropping .3v during load test causing stability issues.
This psu has a 18amp and 19 amp 12v rail so if another supply like an Antec 550w neo HE. has three independent 12v rails each at 18amps wont the 12v line still be stressed because they are independent??
Now the antec true power 500w has 2 rails at 22amps wouldnt this be my best option?

thoughts?

Thanks
June 3, 2006 5:02:43 AM

That 0.3v drop is within the tolerences so it is of no concern.
June 3, 2006 5:03:34 AM

Quote:
basically it comes down to this
I have a d805 and a7900gtx
currently with a ultra xfinity 600w psu but as might be known the d805 is power hungry and speed fan is showing my 12v line dropping .3v during load test causing stability issues.
This psu has a 18amp and 19 amp 12v rail so if another supply like an Antec 550w neo HE. has three independent 12v rails each at 18amps wont the 12v line still be stressed because they are independent??
Now the antec true power 500w has 2 rails at 22amps wouldnt this be my best option?


You need to look at a number of parameters:

-What is the total +12V current rating? (typically it is less than the sum of the individual rail ratings)

-What is each rail assigned to? For example, the new mushkin has four +12V rails, each rated to 20A. Rail 1 supplies the 24 pin ATX. Rail 2 supplies the 4+4 pin CPU. Rail 3 supplies the two PCI-e cables. Rail 4 supplies the opticals, HDs, floppy, etc. But here's the kicker for this PS: if one rail gets flattened by a big load, it automatically bridges rails to meet the need. I've been using one for a few weeks now and it is working like a champ. Not cheap though...

-Look at efficiency vs. load. You can still find units that are in the 65% range at ~50% of full load.

-check out jonnyguru.com for general quality comments and a ton of data. Jonny places Antec in the third tier.
Related resources
June 3, 2006 5:07:30 AM

the NeoHE is a better bet. More total amps and more wattage on the 12v rails.

Also modular, and quiet. i have 1 with an Opteron 146, 6 case fans: 3 have LED's, 2 Barracudas, and an SB Audigy 2 ZS and X1900XT
June 3, 2006 5:09:49 AM

Quote:
That 0.3v drop is within the tolerences so it is of no concern.


It depends in part on what the idle load is. For example, if the +12 is at 11.8 at idle (not at all unheard of) then drops to 11.5 under load, this could present very real problems. Some engineer/designers spec their PS's to run in the 12.05 to 12.1 range under low load so that an ~0.1 or so decrease under load keeps the rail very close to 12.
June 3, 2006 5:30:49 AM

I agree with penguin that the Neo HE is a good PSU. A .3v drop by itself is not large enough to be a problem, but that depends more on the total voltage produced in the first place, as Clue69less pointed out. Measure the total voltage in your present PSU so that you have a good baseline for comparison.

Something that you might be overlooking is heat. If there is too much heat, you will instability no matter what power is being put out by the PSU. A hot CPU or graphics chip will cause problems fast, so find out what temperature those are running at before jumping to conclusions on your present PSU.
June 3, 2006 5:33:06 AM

Quote:
I agree with penguin that the Neo HE is a good PSU. A .3v drop by itself is not large enough to be a problem, but that depends more on the total voltage produced in the first place, as Clue69less pointed out. Measure the total voltage in your present PSU so that you have a good baseline for comparison.

Something that you might be overlooking is heat. If there is too much heat, you will instability no matter what power is being put out by the PSU. A hot CPU or graphics chip will cause problems fast, so find out what temperature those are running at before jumping to conclusions on your present PSU.



WOOT someone got the name right. most ppl mistake the G for a Q since its underlined (damned hyperlink)

kudos
June 3, 2006 5:38:49 AM

Sorry about misspelling your name, Pengwin. My eyes get old and fuzzy and sometimes misread letters. Probably need new glasses.
June 3, 2006 5:40:18 AM

nah, np i blame the forums looks like Penqwin to me too the underline gets in the way.
June 3, 2006 7:07:18 AM



You need to look at a number of parameters:

-What is the total +12V current rating? (typically it is less than the sum of the individual rail ratings)

-What is each rail assigned to? For example, the new mushkin has four +12V rails, each rated to 20A. Rail 1 supplies the 24 pin ATX. Rail 2 supplies the 4+4 pin CPU. Rail 3 supplies the two PCI-e cables. Rail 4 supplies the opticals, HDs, floppy, etc. But here's the kicker for this PS: if one rail gets flattened by a big load, it automatically bridges rails to meet the need. I've been using one for a few weeks now and it is working like a champ. Not cheap though...

-Look at efficiency vs. load. You can still find units that are in the 65% range at ~50% of full load.

-check out jonnyguru.com for general quality comments and a ton of data. Jonny places Antec in the third tier.

my choices are limited to what i can pick up local (san diego)
I do have a Antec Neo 550 HE NIB but i am a little worried about the 12v line

That mushkin psu sound like a good setup. where on jonnyguru are the reviews i only see the current ones in the lower left

The only thing i can figure out
is ultra claims 70 efficiency at full load the 12v line is combined 420w

the antec's 12v is rated at 504w but since they are independent does it matter?

Quote:
That 0.3v drop is within the tolerences so it is of no concern.


It depends in part on what the idle load is. For example, if the +12 is at 11.8 at idle (not at all unheard of) then drops to 11.5 under load, this could present very real problems. Some engineer/designers spec their PS's to run in the 12.05 to 12.1 range under low load so that an ~0.1 or so decrease under load keeps the rail very close to 12.

Under Speefan The ultra idles at 12.05 no load at all. load = 2x prime it drops to 11.75v


Quote:


Something that you might be overlooking is heat. If there is too much heat, you will instability no matter what power is being put out by the PSU. A hot CPU or graphics chip will cause problems fast, so find out what temperature those are running at before jumping to conclusions on your present PSU.


Well i use a corsair nautilus water cooling for the cpu temps are 65~67° after a few hours of prime95. The video card idles at 45° I dont think it breaks 60°


Thanks everyone for your help.
June 3, 2006 2:36:59 PM

Quote:
my choices are limited to what i can pick up local (san diego)


I'd think you could find plenty of options there.

Quote:
where on jonnyguru are the reviews i only see the current ones in the lower left


On the lower right he has a few links to some generalized comparisons. Somewhere in there are more specific PS reviews. It's a good site to take the time to surf around and get to know. I don't see much in the way of bias in his reviews, just strong opinions and dat are otay.

Quote:
Well i use a corsair nautilus water cooling for the cpu temps are 65~67° after a few hours of prime95. The video card idles at 45° I dont think it breaks 60°


All temps are C? I wouldn't want to run at 65C myself. Sure, people have run alot hotter and survived (a while) but I want load temps at ~50 and below.
June 3, 2006 3:34:46 PM

thats really hot for *C or really good for degrees *F
June 3, 2006 5:51:18 PM

Thanks Clue69less for the johnnyguru link. Very interesting and worthwhile reading about PSU design and testing! Learned more there in about 90 minutes reading than I have in years of reading PSU reviews by other folks.

-Bob
June 3, 2006 5:58:58 PM

Quote:
thats really hot for *C or really good for degrees *F


Its 67°c and from research around the web thats a good normal oc temp for it.
June 3, 2006 7:58:34 PM

depends how much u hav eOC'ed that 805D
June 4, 2006 4:12:21 AM

Quote:
Thanks Clue69less for the johnnyguru link. Very interesting and worthwhile reading about PSU design and testing! Learned more there in about 90 minutes reading than I have in years of reading PSU reviews by other folks.


You're welcome, Bob. If anyone out there has any good technical stuff on modern PC PS design, I'd appreciate some links. I'm not particularly strong regarding circuit analysis but it's time I get into it more.
June 4, 2006 9:52:57 PM

i have it at 3.98ghz 67° after about 4hours of dual prime , its fine for me. i craked the ihs on this 805 so i dont think thst helps.
Well i just did the volt mod on my mobo so if i still have the 12v issues i will throw on thw antec neo 550.
June 5, 2006 12:11:04 AM

ok i guess thats ok for 3.98 ghz.
!