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What is "Amp Amp"?

Last response: in Graphics & Displays
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September 10, 2007 5:00:28 PM

I was looking to upgrade to a new video card, reading the specs from eVGA's 8800 GTS with 640MB (non-OC version). It recommends +12V with 26 Amp Amp! :heink:  What is that mean? How does that translated into Watts for the PSU?

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September 10, 2007 5:37:55 PM

eman6628 said:
I was looking to upgrade to a new video card, reading the specs from eVGA's 8800 GTS with 640MB (non-OC version). It recommends +12V with 26 Amp Amp! :heink:  What is that mean? How does that translated into Watts for the PSU?


power supplies have amp ratings on their +12v written on the side of the PSU.

If you don't have a recent power supply you won't be able to run it.
September 10, 2007 6:49:25 PM

I know about the seperate +12V rating on the current generation of PSU. The highest max load on +12V I have seen is about 18A on a 1000 Watts PSU. So I still don't know what this "26 Amp Amp" is in reference to!
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September 10, 2007 7:10:13 PM

Maximum wattage on combined 12v rails
divided by 12 = amps
For example: my Dell 305w psu has 22amps
12vA 18a + 12vB 18a
264watts maximum on the combined 12v rails
264 divided 12 = 22

20a I believe is the max for a single 12v rail
You do not just add 18a + 18a = 36amps-INCORRECT biggest mistake people make

The 8800GTS 640 says 26amps (unless a heavy system load)

http://www.tigerdirect.com/applications/SearchTools/ite...

Minimum System Requirements

1GB of system memory

CD-ROM drive

50MB of available hard disk drive space for basic driver installation

Microsoft Windows XP operating system

PCI Express-compliant motherboard with one vacant PCI Express x16 slot

400W PCI Express-compliant system power supply with a combined 12V current rating of 26A or more
September 10, 2007 7:37:17 PM

Ok, so it is the combined ampere of both +12V lines! That makes more sense why it is spec'ed at 26 Amp Amp, but it is rather confusing, as one of the +12V line (or rail) is supposely for the CPU and the other for the MB and peripherals, which to me only 1 of the line is to provide power to the video card.
September 10, 2007 7:45:41 PM

No. Cpu, gpu, and hdds on the 12v
September 10, 2007 8:06:36 PM

ok thx for answering!
September 10, 2007 8:40:22 PM

oh, and getting the bare minimum to run is not a good idea, the parts will die faster
a b U Graphics card
September 10, 2007 9:42:55 PM

kpo6969 said:
Maximum wattage on combined 12v rails
divided by 12 = amps
For example: my Dell 305w psu has 22amps
12vA 18a + 12vB 18a
264watts maximum on the combined 12v rails
264 divided 12 = 22

20a I believe is the max for a single 12v rail
You do not just add 18a + 18a = 36amps-INCORRECT biggest mistake people make

The 8800GTS 640 says 26amps (unless a heavy system load)

http://www.tigerdirect.com/applications/SearchTools/ite...

Minimum System Requirements

1GB of system memory

CD-ROM drive

50MB of available hard disk drive space for basic driver installation

Microsoft Windows XP operating system

PCI Express-compliant motherboard with one vacant PCI Express x16 slot

400W PCI Express-compliant system power supply with a combined 12V current rating of 26A or more


How is adding the combined amps on the +12v rails a big mistake?
I've got a old psu laying around and it says this
+12v1 @ 8A
+12v2 @ 13a

Wattage on
+12v1 96w
+12v2 156w

Total wattage on combined +12v equals 252w
96+156=252

252/12=21

Now is that the same as just adding both the +12v rails?
+12v1 @ 8A
+12v2 @ 13A

8+13=21
September 10, 2007 9:57:03 PM

Because in most cases it doesn't work like that. Take the Corsair HX620:

+12v1: 18amps
+12v2: 18amps
+12v3: 18amps

Total watts on the +12v rails 600w.

600/12=50

18+18+18= 54amps

Generally, when they say 18 amps for each rail it means that each rail can individually support 18 amps at one time, but not all three at once.

a c 114 U Graphics card
September 10, 2007 10:12:34 PM

26 Amp Amp sounds like a typo

and amp is a measurement of electrical current

You get it by taking W(wattage) and dividing it by V(Voltage)

You get wattage by A(amp) times V(voltage)

So 26Amps 12 x 26 = 312watts of 12 volt power

Thats allot(for just a video card) of power and the 26 takes into consideration a fairly high end system(high end board X6800 ect) as a 8800GTX only takes 150watts to run it.

edited to remove confusing example....
a c 365 U Graphics card
September 10, 2007 11:31:37 PM

Devices running off the 12v rails:

1. CPU
2. GPU
3. Hard Drive (the read / write heads use the 5v rail)
4. Optical Drives (the read / write head uses the 5v rail)
5. Fans

a c 114 U Graphics card
September 11, 2007 5:54:12 AM

kpo6969 said:
What about the cpu and HDD's? 12v I believe.
BTW: The 8800GTX uses 132 watts. If you throw numbers around try to be more accurate.

http://www.atomicmpc.com.au/forums.asp?s=2&c=7&t=9354


With so many OC'd out of the box i tend to give it a little more to the video card. better to be safe...

My full system never draws more then 350 watts at the plug....so - 20% for AC to DC conversion and step down/regulation and the system draws 280 watts....so the 26 amps IS quite a bit

Case: Antec 900(4 120mm fans and 1 200mm fan)
PSU: OCZ 700watt
Board: P35 DS3R
CPU: Q6600 @ 3.00
CPU cooling : Zalman 9500 @ ~2200 rpms
Memory: 2x 1024MB ,2X 512MB @ 2.0 volts 4-4-4-10
Video: 8800GTX 600(core) 1400(shader) 900 x2(memory)
Storage:
2x WDC 250gig (Raid0)
2x Seagate 320gig(Storage)
2x Seagate 500gig(Storage)
Optical drive: Samsung SH-W162
TV card: PVR 250
Sound: Creative SB Audigy 2zs
a b U Graphics card
September 11, 2007 6:18:24 AM

kpo6969 said:
20a I believe is the max for a single 12v rail

According to the ATX standard, but some manufacturers (particularly PCP&C) don't follow the standard correctly. They have some very high amperage single 12V rail PSUs. Generally though, multi 12V rail PSUs do follow the standard in this regard.
September 12, 2007 3:36:22 PM

randomizer said:
According to the ATX standard, but some manufacturers (particularly PCP&C) don't follow the standard correctly. They have some very high amperage single 12V rail PSUs. Generally though, multi 12V rail PSUs do follow the standard in this regard.



yup, I believe its 60 amps on a sinlge +12V rail.

Iv seen something similar on some of the silverstone psu's aswell.


edit: hehe....90amps on a single +12V rail -> http://www.silverstonetek.com/products/p_contents.php?pno=op1200&area=
September 12, 2007 6:08:19 PM

randomizer said:
According to the ATX standard, but some manufacturers (particularly PCP&C) don't follow the standard correctly. They have some very high amperage single 12V rail PSUs. Generally though, multi 12V rail PSUs do follow the standard in this regard.

My bad, you're correct. I should of said single 12v rail of multiple rail configuration. Thanks
a b U Graphics card
September 13, 2007 5:13:19 AM

No prob ;) 
September 13, 2007 5:42:17 AM

randomizer said:
According to the ATX standard, but some manufacturers (particularly PCP&C) don't follow the standard correctly. They have some very high amperage single 12V rail PSUs. Generally though, multi 12V rail PSUs do follow the standard in this regard.
Many don't follow the ATX12V standard even thought they claim that they do. One offender I found recently is Corsair. They even have it on the sticker on the side of their PSU 18A per rail. That is a little disturbing.

PC Power and Cooling don't claim to be ATX12V compliant, they claim to be EPS12V compliant and clearly state, and even boast, that they use a large single 12V rail.
a c 114 U Graphics card
September 13, 2007 6:20:57 AM

Most PSU's just use virtual rails to claim multi rail. OCZ does it too(FSP since they make the psu as well)

The advantage....you are not "wasting" the extra power on other rails like some people think...since its just one big rail and they just separate it on the board(in on the wires in some cases) in a way that it all still comes from one location with a massive single rail anyway.
September 13, 2007 7:21:06 AM

Well the virtual rail thing is just marketing. If each rail isn't limited to 240VA then it doesn't meet the ATX12V standard and they shouldn't claim that it does. And they most certainly shouldn't claim that each rail is current limited to 18A on the PSU sticker if that is not the case.

Don't get me wrong I have a Silencer 610 and I bought it specifically for the 49A single rail. PSU companies should just be honest. Some people want the 20A/240W per rail limit for safety reasons.
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