Author Topic: Power supply question..... (Read 287 times)

humble · « **on:** April 13, 2006, 06:26:26 PM »

I posted a seperate thread on my rack box below....all I'm going to due (for now) is throw in a better video card. Below I asked the question on power supply and got back a very good answer from 38ruk (thanks BTW). Armed with his 411 regarding amps on the 12v feed I browsed 3 diff local PC places today....looking at 400w to 600w PS's...98% had 18a 12v+ ratings....none had the 20a 38ruk suggested. Now my rack box has a 300w PS....but a 19a 12+ line....total draw is well under the 300w.

I've built 50? box's and always put a 430w or better and have 3-4 boxes here I could canibalize as well....none of them have 20a 12v lines either....

So what really matters here...the pure Watts or the Amps on the 12v+ line or both????????

thanks

Kev367th · « **Reply #1 on:** April 13, 2006, 06:37:32 PM »

Both matter. (especially for latest video cards)

A good quality PSU with dual +12v rails will each have 18-19+ Amps EACH.
A good quality PSU with single +12v rail will put out 36-40+ Amps.

Best dual I've come across put out 22 Amps on each +12v rail, most around 18-19.

humble · « **Reply #2 on:** April 13, 2006, 06:54:32 PM »

I'm guessing this is a dual 12v at 19a...looking around I have 1 450 at 21a but it doesnt have a sata power lead (that I saw anyway). NP going to buy one if need be....just curious....it looks like the 7900GT pulls about 170w under full load so I'll need to add stuff up....just cant see using a 300w PS in a system regardless.

Kev367th · « **Reply #3 on:** April 13, 2006, 07:28:05 PM »

I use an Emermax Liberty 500W PSU

Modular cables (only plug in the ones you need)
+3.3V@28A, +5V@30A, +12V1@22A, +12V2@22A, -12V@0.6A, +5VSB@3A (dual +12v @ 22amps each)
2 dedicated PCI-E cables / sockets

http://www.newegg.com/Product/Product.asp?Item=N82E16817194003

humble · « **Reply #4 on:** April 13, 2006, 07:30:19 PM »

found an interesting article regarding PS sizing...mirrors what alot of my "tech friends" say {I live in development that is 10%+ intel folks}....PS article

Aso found a pretty good PS calculator (not current on latest cards)

PS calculator

I found the spec sheet on the PS in the box. Actually a pretty nice PS....but not the one they needed. whats funny is that the "correct one" {that gateway uses for ex) is almost the same price but has 2 12 rails and extra connections....simply one more reason to avoid the HP/Compaq's if you consider a rack box....to include "upgrability" and not provide a PS adaquate to the task is bad business.......

Current PSA specs

38ruk · « **Reply #5 on:** April 13, 2006, 09:52:30 PM »

Here is an article than compares power usage of the 7900GT , sorry if youve already seen it. Note that the wattage is for the whole pc . Humble that 300W PS suprised me in the amp department , If it doesnt have alot of other power consuming devices you "might" be OK 38
http://www.guru3d.com/article/Videocards/326/4/

humble · « **Reply #6 on:** April 14, 2006, 01:35:47 AM »

great link.

The rack box is basically a HTPC. I'm pretty amazed how good it is overall however it has xpress 200 (ATI) instead of the 6150 onboard video the nvidia based 939 boards have....otherwise you could run purevideo on it and it would be great for everything but gaming. Since I'm going to be driving a 37" 1920*1080 res "monitor" I'm a bit concerned about the total overhead....but the PS does have a pretty good spec sheet for a 300w box but the pisser is the same company makes a 300w PS with dual 12v 18a lines....

the right PS

and its about the same price