CPU Amperage requirements

[locane]

All right, I need help.

I recently purchased an Asus Crosshair, an AMD 6400+ Black edition, and two sticks of corsairs ddr2 800 that is tested and rated for my motherboard.

Asus is telling me all kinds of crazy crap about the amperage requirements on the Crosshair, and I need to bounce these numbers off you guys to see if they are sane.



First Asus tells me:

what you will want to make sure of is that the power supply you choose to go with can put
out a minimum of 28 amps on the +3.3 voltage rail which powers up your cpu and your agp slot, a
minimum of 30 amps on the +5 voltage rail which powers up all of the IC chips on the motherboard
and a minimum of 18-20 amps on the +12 voltage rail which powers up all of your drives and fans

The board is dual PCIE, by the way. Apparently this guy didn't know that.

I wrote back and told them that I couldn't find any power supplies with the minimum amperage requirements they listed, especially on the 3.3v rail. Then they tell me this:

---------- Original Message ----------
From:ASUS TSD
To:locane@gmail.com
Date:2007-11-21 00:35:03

On a PSU this is what I will always recommend...

550 Watt Min.

+3.3V = 30A
+5V = 35A
+12V = 40A Combined Total.

Best Regards,

Rob
Level 3 Support Engineer
Asus Technology
Http://usa.asus.com
Phone: (812)-282-2787
RMA: (510)739-3777 opt. 2

So I go looking, again. Nothing. Seriously, find me a power supply that exceeds those amperage requirements.

I found 1. One. Silverstone's OP1200 with 40 / 40 / 90 amperage on the 3.3, 5, and 12v rails respectively. It's $380.

I'm planning on overclocking this board and cpu, and probably dropping AMD's Phenom into it when it comes out.

Do I seriously need more than 30 amps on the 3.3v rail to support this? Does anyone have a system similar to mine that is running off of a weaker power supply?


Thanks for all your help in advance. Dealing with Asus has been really frustrating.

--Locane

 

[Gravemind123]

Here is the list of combined +12v amps on PSUs: http://forums.guru3d.com/showthread.php?t=205763

As for 3.3v and 5v rail, they aren't all that important when compared to the +12v rail, which is where most of the graphics, CPU and drive power will come from. Also, the requirement for power isn't based on the motherboard so much as what is in it. Your graphics card(s) will be the biggest factor in determining your power requirement, then CPU, then number of drives and motherboard.

Realistically, if you don't run more then one video card, you won't need more then a good quality 450W, even with an 8800Ultra. If you run dual-8800Ultras, you would probably want about a good 600W range power supply.(A single 8800Ultra in a system with a Core2Extreme X6800, 4GB of ram, a single SATA drive and a 680i SLI board uses only 320W at load)

If you want a good power supply, try looking at Corsair, SeaSonic or PC Power and Cooling and find one in the range of what you will likely use.

 

[Zorg]

The Silencer® 610 EPS12V Power Supply will run that board with room to spare.

It's on sale at Newegg for the same price right now.

 

[RetiredChief]

Grvemind123, Your main point is 100% on - The main consideration is the +12V rails baised on the GPU requirements.

One point - CPU power is not derived from +12V, but from the 3.3 V Rail normally (For 1V -> 2V) processors.

Locane, I would think that a rating of 20A (3.3V) and 20A (+5V) (Combined rating for 3.3V & 5V of 160W) would be sufficient

The reason for the combined rating is that the +5 and the +3.3V come from the same source and you cannot have both at max rated output.

Edited - Concur with Zorg. Specs show 30A (+5V) and 24 A (+3.3V)