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Which PSU To Get For 7900GT That's 12V@20A

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aznnerdwannabe

Junior Member
Which PSU Should I Get For The XFX 7900GT That Has 12V@20A As They Stated. I Checked All The Antec's And The Max Was 12V@19A. Called Both Company But They Told Me That My System May Be Unstable Or It Won't Function Correctly. I Checked Ohter Brands And They Varied From 12V@17A To 12A@19A.

May You PLEASE HELP ME Find A PSU with 12V@20A.
Thank You So Much In Advance.
 
My dual rail Blue Storm works just fine with my 7900GT. It's 15A on each 12V rail. The power reqirements can't be too crazy apparently.
 
Originally posted by: aznnerdwannabe
Which PSU Should I Get For The XFX 7900GT That Has 12V@20A As They Stated. I Checked All The Antec's And The Max Was 12V@19A. Called Both Company But They Told Me That My System May Be Unstable Or It Won't Function Correctly. I Checked Ohter Brands And They Varied From 12V@17A To 12A@19A.

May You PLEASE HELP ME Find A PSU with 12V@20A.
Thank You So Much In Advance.
Click to expand...

Welcome to AT.

1) Please Do Not Capitalize Every Word In Your Posts. It Is Very Hard To Read And Makes It Look Like You Do Not Know How To Write In English.

2) There are many, many, many, MANY PSUs with more than 20A of current available on their +12V lines. Many of the high-end models have multiple +12V rails; this one, for instance, has two +12V rails with 19A each, or a total of 38A.

3) Please check out the PSU thread that is stickied in the General Hardware forum. It has a lot of good information.
 
Originally posted by: Alaa
its safe also to get a psu with 12V1@19A & 12V2@19A ,right?
Click to expand...

Not if you are sure that you need 20A from one of those two rails and the 2 12V rails are completely isolated (if you can get only 19A from one rail even if the other rail is not loaded at all).
 
Originally posted by: Navid
Originally posted by: Alaa
its safe also to get a psu with 12V1@19A & 12V2@19A ,right?
Click to expand...

Not if you are sure that you need 20A from one of those two rails and the 2 12V rails are completely isolated (if you can get only 19A from one rail even if the other rail is not loaded at all).
Click to expand...

so they r isolated or it differs from one to another?
 
Originally posted by: Alaa
Originally posted by: Navid
Originally posted by: Alaa
its safe also to get a psu with 12V1@19A & 12V2@19A ,right?
Click to expand...

Not if you are sure that you need 20A from one of those two rails and the 2 12V rails are completely isolated (if you can get only 19A from one rail even if the other rail is not loaded at all).
Click to expand...

so they r isolated or it differs from one to the other?
Click to expand...

I have no direct experience on this. So, I cannot answer your question and will wait for someone else to reply.

But, I expect the reason for having two rails instead of one (two 19A rails instead of one 38A rail for example) is to make the manufacturing easier and cost effective. A rail that can handle 39A requires safety precautions that may be costly.

Separation also offers noise isolation so your system can be more stable by placing your sensitive components (CPU) on one rail and noisy components on the other.

Both of these require complete isolation, which would not allow the load to be shared.
 
Originally posted by: Navid
I have no direct experience on this. So, I cannot answer your question and will wait for someone else to reply.

But, I expect the reason for having two rails instead of one (two 19A rails instead of one 38A rail for example) is to make the manufacturing easier and cost effective. A rail that can handle 39A requires safety precautions that may be costly.

Separation also offers noise isolation so your system can be more stable by placing your sensitive components (CPU) on one rail and noisy components on the other.

Both of these require complete isolation, which would not allow the load to be shared.
Click to expand...

There's some question how well-"isolated" the rails on most dual-rail PSUs actually are.

But in any case, it would not be a big problem for a system with one GPU -- put the graphics card on one rail, and everything else on the other one. 19A@12V is 228W, which is PLENTY for any single modern video card (unless you want to overvolt and phase-change cool it, maybe).

Where you can get into trouble is if you want to do SLI/Crossfire with two very fast cards; you can't put them both on one rail that only does 15-20A, and since the CPU/motherboard is usually wired into one rail, you may have trouble putting even one fast graphics card (that pulls 125+W) on the same +12V rail as a fast CPU (which can also pull over 120W). At that point, you either need to go to a PSU with three or more independent rails, or one with just one very beefy +12V rail that can push 30A or more.
 
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