psu overkill?

[Washoe]

I've got a Sapphire X1900XTX card on the way from newegg but I also need to choose a psu to upgrade into. I don't think my current Thermaltake 500w will handle it (29 total A on the 12v rails).

So I'm looking into the FSP Group 600 watt PSU. The thing appears to be a real beast:

link

The thing is, this PSU has got four 12v rails!! I'm wondering if this is going to be too much for my system. Current specs in my sig, plus I'll be adding the X1900XTX card. In looking over the FSP psu specs, it seems that the 4th rail is only to be used for a second PCIe card, either for CF or SLi. I will not be doing either CrossFire or SLi, I'll just be using the 1 card. Would it be a waste to go for this PSU? Are there any drawbacks to getting a psu with 4 12v rails, where the 4th one won't even be used? Thanks for any comments!

 

[BassBomb]

how many hds? get an enermax liberty 500

 

[1Dark1Sharigan1]

No such thing as "PSU overkill" (well unless we're talking like 850W or 1KW PSUs) for systems with modern CPUs, GPUs, etc. Better safe than sorry.

 

[thilanliyan]

I think it probably is overkill. In my sig, everything is running overclocked except the ram and added to that the watercooling, 1 SCSI and 2 SATA HDDs, and 2 DVD burners and all run on a 420watt OCZ Powerstream PSU and it's very stable. I think your 500w should handle it fine. Unless ATI recommends a huge amperage on ONE 12v rail.

 

[Washoe]

Originally posted by: 1Dark1Sharigan1
No such thing as "PSU overkill" (well unless we're talking like 850W or 1KW PSUs) for systems with modern CPUs, GPUs, etc. Better safe than sorry.

Usually I also feel that way however this seems like it may actually be a case of overkill. I run 2 internal IDE drives (both 7200 RPM), and 1 external USB-connected backup drive. 2GB RAM, 1 DVD/CD burner and that's about it.

I like the security of having a monster psu though. I would feel pretty assured that any near-future problems would not be psu related anyway ...

still undecided at this point.

 

[duragezic]

I don't see a need for a new PSU.

500W is plenty unlesss as stated the amperage for a separate rail is insufficient with ATIs recommendation.

Look at Anand's X1900XTX reviews. He has a more powerful rig (2.6ghz FX-55) yet his Power tests show Load for a Connect3D 1900XTX as only ~335 W. I think your 500 W (that may output 450 W max or so) is plenty.

 

[jiffylube1024]

29A on a PSU's single +12V rail should be enough, but Thermaltake usually overrates their PSU's by a bit. Also, is this your PSU (two +12V rails: 14A and 15A?) . If so, then that PSU does NOT have 29A on the +12V rails (unfortunately, you do not add the two to get combined power). If that is your PSU, then you should upgrade - there has already been reports of someone having problems with that PSU and a X1900XT.

Look for PSU's with dual 18A +12V rails or better or a single 28A +12V rail or better.

 

[Washoe]

Originally posted by: jiffylube1024
29A on a PSU's single +12V rail should be enough, but Thermaltake usually overrates their PSU's by a bit. Also, is this your PSU (two +12V rails: 14A and 15A?) . If so, then that PSU does NOT have 29A on the +12V rails (unfortunately, you do not add the two to get combined power). If that is your PSU, then you should upgrade - there has already been reports of someone having problems with that PSU and a X1900XT.

Look for PSU's with dual 18A +12V rails or better or a single 28A +12V rail or better.

Thanks for the comments, yes that is my current psu (and possibly that was my post about a week ago, about the report you were thinking of).

I believe 30A is the recommended for the X1900XTX card, but I thought you could combine the amps on the 12v rails to reach the recommended total. This is actually not true?

 

[BassBomb]

the card itself wont take 30A like they say, rail splitting usually one is like cpu and video the other is perpherials... so i dont know... 18A x 2 rails is good (even i have that)

 

[Elfear]

My brother is buying the exact PSU you're asking about for his X1900XTX. We thought his 450W E-power (supposedly same internals as the 450W Modstream) would do the trick with 28A on the 12V rail but everytime he starts a 3D app he can hear his case fans start to slow down. It's kinda funny really. I can post some results by next week if you want me to.

 

[Ronin]

Saw the same thing happening with a TT 680W. Put in a S12-600, and everything's been solid since.

Go with the FSP. It's a good choice.

 

[Washoe]

Thx alot everyone for the input. I'm still slightly confused about something - The ATI recommendation is 30A on a 12v rail, yet this FSP psu I'm looking at is showing 15A on each 12v rail. How can that possibly supply the recommended 30A?

 

[n7]

The video card itself doesn't suck up anywhere close to to 30A.

The 30A ATi is wisely recommending is based on a single 12V rail, which means that is including everything in the PC.

Here i quote an FSP employee on another forum:

Originally posted by: [FSP] Grace
...here is the info on the 12V rails. Hope this helps.
12V1 - CPU 1
12V2 - CPU 2, PCIe 2
12V3 - Motherboard, SATA, 4-pin molex
12V4 - PCIe 1

...Yes, the present ones have been reclassified. Even though it says 15A, it's actually 18A (with Over Current Protection of 20A).

The FSP will be more than adequate for your needs

 

[Skott]

I notice that alot of the PSUs have dual rails and I seen a Silverstone 650w psu over on the Monarch configurator that has quad 12v rails. Part of Silverstone's 'Zeus' series. What exactly does having quad rails offer over a dual rail psu? I mean besides the obvious extra two rails? I think my problem is that I dont exactly understand what the rails do. I know they have to be stable and I know having dual rails is considered better than a single rail when it comes to SLI/Crossfire setups. Can someone put it into layman terms for me?

Thanks,

Skott

 

[Dethfrumbelo]

Dual rails are supposed to isolate major components like CPU/GPU from current fluctuations/ripple caused by HDDs/Fans (especially the startup surge/drop) or other high pull components, providing a cleaner signal.

Most dual rail PSUs should be able to handle 1 video card (15A should be enough). Dual cards would probably be difficult for one 15A rail, depending what else was on it.

What other components are generally on the rail to video? Must be HDDs and Fans, because I think they want the cleanest signal to the CPU.

 

[Elfear]

While I generally never recommend a dual rail PSU for just the reasons mentioned above, the FSP unit is a little different than most. While each of the four 12V lines is rated at 15A, any single line can be loaded up to the max amps of what the four combined would be. That doesn't mean 15A x 4 or 60A, but it means that the max amps that the 12V line can give (which I believe is 42A for the 600W FSP) can go through one of the 12V rails. A smart move on FSP's part (probably other manufacturers who do the same thing).

Here's a good read about it's big brother that gives a lot better explanation than I just did.

 

[Capt Caveman]

I have a Seasonice S12-500 w/ dual 12v rails of 18A and 17A. My guess is ATI Tool's "GPU Current Draw" meter is totally off b/c in 2D mode it lists 5.5A but in 3D mode it hits 24.5A(obviously wrong). I haven't seen any other program that provides this function, does ATI Tool just make it up or use some kind of algorythmn?

 

[Elfear]

Originally posted by: Capt Caveman
I have a Seasonice S12-500 w/ dual 12v rails of 18A and 17A. My guess is ATI Tool's "GPU Current Draw" meter is totally off b/c in 2D mode it lists 5.5A but in 3D mode it hits 24.5A(obviously wrong). I haven't seen any other program that provides this function, does ATI Tool just make it up or use some kind of algorythmn?

I noticed the same thing. When I raise the voltages a bit, ATI Tool says that my card is drawing 33.5A at load. Hope they get that figured out as the real amp draw would be very useful.