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PSU for x1950xt 256mb

MuSsEr

MuSsEr

MuSsEr

Associate
Joined
26 Jun 2005
Posts
1,135
Hi,

I'm buying my gf a better gfx card for xmas as her 6600gt is getting a bit long in the tooth now

she has the following:
A64 3200+
Abit AN8 motherboard
4 x 512mb corsair Ram (2gig)
40gig hdd
2x 200gig hdd

and will have an x1950xt

She currently has an Antec 480watt PSU

Will this psu be ok for this set up?
Is the wattage enough?
Does it have strong enough 12v rails?
What sort of ampage per rail does the x1950xt require?

Lots of advice please as I don't wana get it for her then say "actually, sorry you'll have to wait to use it as your PSU isn't good enough"
 
I have been reaidnt his PSU needs a 450watt or greater with 30amps on the 12v rail

the antec is 480watt and has 2x 12v rails...
one is 18amps and the other is 15amps

I'm not quite sure what split 12v rails actually do or what their purpose is

and it says 450watt min....does that mean just for the gfx card? or is it taking into account the fact its going to be inside a pc and what the average pc uses in wattage as well?

PSU calculator says the rig should require about 380watt.....but I'm not entirely trusting of that

(p.s. i dont want this thread to turn into a stupid debate about how 350watt psus can run 8800gtx and that 1.1kw psus are a watse of money coz i dont really care for your opinions on those matters)

I'm after some solid facts from people who actually know what theyr talking about please :)
 
I asked the same question a while back and got told that I should have at least 18a on each rail. I know next to nothing about PSU's, which is why I posted here. My advice to you though is to wait untill someone more knowing than me replies.

Just letting you know though that I've gone for a PSU with 18a on each 12v rail :)
 
would also be interested to hear from people with real experience of these cards i have read some people are having real problems with the saphire cards over at there forums


http://www.sapphiretech.com/en/forums/forumdisplay.php?f=4


the people there are saying only use certain types of psu put me right of getting that version i am looking at other makes with better heatsinks now as it may not be a power issue but a heat problem although they refuse to admit that over there

i can understand needing a very exclusive psu for the latest and greatest card but not for a mid-high range card
 
http://www.extremeoverclocking.com/reviews/cases/Antec_TPII-480Blue_4.html

This one?

Then it can supply up to 33A/396w combined 12v current/wattage. That means it can supply 18A to either rail. But not both at the same time. So 18A+15A or 16A+17A or 15A+18A etc. Get the picture?

The ATi 450w spec is for the total system. More importantly the XT may use up to what? 10A/120W @ 12v. So your PSU has plenty, It'll work fine.
 
30a on the 12v Rail, are they that powerfull then, ive only got 1x 12v rail with 20a on my PSU, and its powering my x1800 XT 512mb no sweat, surely the x1950 can't use that much more, they are supposed to use less than the x1900's.
 
MuSsEr said:
Not sure this is correct, don't know many PCs with 30A 12v rails, most have split 12v rails with like 24a or less on

my 580watt hiper has split 12v rails and powers 2x 7800gtxs and it only does something like 20a per rail
Click to expand...
Where did I say it had one rail? Notice the work combined? 99% of PSU's feed from the same source, I'm generalising because there are a few exceptions. But a rail is in fact a current limiter set to stop a particular connection from pulling more than 240VA. Both current limiters are connected to the same primary. In power supply terms the figure that matters is the maximum combined 12v wattage. As for power supplies that have single rails, i.e its the same as the dual rails, just no overcurrent limiter to get in the way, they do exist I have one of the best ever made.

thiper20315if.jpg


Take the Hiper you mention. Two rails 18+20=38A or 456W. Er..no, more like 30A total.

Confused about Dual Rails? This may help with the usual misconceptions.

http://forums.silentpcreview.com/viewtopic.php?t=23916
http://www.silentpcreview.com/article28-page1.html


It's important to remember that even though there are two "independent" 12V lines, they still draw from the same main source. It's highly unlikely that there are two separate 120VAC:12VDC power conversion devices in a PSU; this would be much too costly and inefficient. There is only one 12VDC source, and the two lines draw from the same transformer. Each line is coming from the same 12VDC source, but through its own "controlled gateway".

PSU makers' specs are misleading in that thay rate the current capacity of each 12V rail independently. What really matters is the total 12V current: Generally, up to 20A is available on any one 12V line assuming the total 12V current capacity of the PSU is not exceed.
Click to expand...
 
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fornowagain said:
Where did I say it had one rail? Notice the work combined? 99% of PSU's feed from the same source, I'm generalising because there are a few exceptions. But a rail is in fact a current limiter set to stop a particular connection from pulling more than 240VA. Both current limiters are connected to the same primary. In power supply terms the figure that matters is the maximum combined 12v wattage. As for power supplies that have single rails, i.e its the same as the dual rails, just no overcurrent limiter to get in the way, they do exist I have one of the best ever made.
Click to expand...

I didnt mean by what I said that you said it had only one rail, I meant that when you were saying they would provide about 15amps and 18amps that that would not be enough for a x1950xt as neither rail is 30amp....but I dont know many psus with 30amp rails, most have split rails
 
MuSsEr said:
I didnt mean by what I said that you said it had only one rail, I meant that when you were saying they would provide about 15amps and 18amps that that would not be enough for a x1950xt as neither rail is 30amp....but I dont know many psus with 30amp rails, most have split rails
Click to expand...

Reading that very carefully. Are you thinking an XT needs 30A? I'm telling you that you can't get more out of the 2 rails than goes in. Each rail has an upper limit. The total current that can be supplied depends on the common source. And that is defined as the "combined maximum 12v wattage".

It doesn't matter which rail the graphics card is connected, neither will be overloaded by the card. Typically the XT will use 10A/120W at 12v. The rails are named 12v1 & 12v2

12v1 may be well assigned to the motherboard and CPU, 12v2 could feed the peripherals and PCIe connectors if it has them. Depends on how its designed.

The strictest reference to ATX2.2 spec would have the cpu assigned to 12v1 exclusively, that's rarely implemented.

The form factor ATX spec for rails is 240VA, a few have stretched it to 22A. In reality the current limiter usually goes a bit higher. You will find a few PSU's without current limiters set to values less than the total capacity of the primary. Or simply put, one large rail.

72A Single rail example. You did say you wanted to know a bit more!!
 
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MuSsEr said:
yep, s'all useful thanks

how come the specs for x1950xt from ati say "min 450watt 30amp 12v rail" then?
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Ah I see your confusion, thats the system requirement!!! And the 30A is the combined value I explained earlier.
 
I just bought a X1950XT and i'm using it with a C2D 6400, 2 sata drives, 1 optical drive, 2 sticks of DDR400 ram, several fans, and a Dual-VSTA mobo and it's all powered by a 430W Antec Truepower.

I think it's just hanging in there tbh as sometimes in games my pc lets out a prolonged beep for a few seconds which i can only assume is the mobo telling me that the 12V rail is dropping when the gfx card pulls a lot of current.

So 480W should be ok as long as nothing is overclocked. If overclocking i'd want nearer 600W i think.
 
dodgem said:
I just bought a X1950XT and i'm using it with a C2D 6400, 2 sata drives, 1 optical drive, 2 sticks of DDR400 ram, several fans, and a Dual-VSTA mobo and it's all powered by a 430W Antec Truepower.

I think it's just hanging in there tbh as sometimes in games my pc lets out a prolonged beep for a few seconds which i can only assume is the mobo telling me that the 12V rail is dropping when the gfx card pulls a lot of current.

So 480W should be ok as long as nothing is overclocked. If overclocking i'd want nearer 600W i think.
Click to expand...
Buy yourself a multimeter for a tenner, if you don't already have one and find out for sure.
 
dodgem said:
I just bought a X1950XT and i'm using it with a C2D 6400, 2 sata drives, 1 optical drive, 2 sticks of DDR400 ram, several fans, and a Dual-VSTA mobo and it's all powered by a 430W Antec Truepower.

I think it's just hanging in there tbh as sometimes in games my pc lets out a prolonged beep for a few seconds which i can only assume is the mobo telling me that the 12V rail is dropping when the gfx card pulls a lot of current.

So 480W should be ok as long as nothing is overclocked. If overclocking i'd want nearer 600W i think.
Click to expand...

thats useful thanks, my missus is only running a A64 3200+ cpu which i suspect draws quite a bit lett can your C2D, and she does not overclock

so i suspect x1950xt might be fine :)
 
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