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Author Topic: Dell PSU  (Read 15717 times)
aznstriker92
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« on: March 01, 2008, 08:30:03 PM »

What do you guys think about Dell Powersupplies? I have a 305 watt with 22amps on dual 12v. Anybody think I can push a 8800GT? I heard Dell underrates their psus too.
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Eliot
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« Reply #1 on: March 03, 2008, 06:07:37 PM »

What do you guys think about Dell Powersupplies? I have a 305 watt with 22amps on dual 12v. Anybody think I can push a 8800GT? I heard Dell underrates their psus too.

why not?

depands on your configuration, but Dell does not stuff their machines with lots of harddics....
For reference check out this:
http://www.fudzilla.com/index.php?option=com_content&task=view&id=5871&Itemid=40&limit=1&limitstart=3


best,

Eliot.
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aznstriker92
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« Reply #2 on: March 04, 2008, 11:48:09 PM »

Well I was just worryed about not having enough amps.
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Jon
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« Reply #3 on: March 05, 2008, 05:35:47 AM »

It's a tough call really.  When I modded my Dell Dimension 8400 two years back and put in an ASUS P5LD2 mobo, I had to swap out the PSU for a 3rd party one (Ultra X2 550w) just by doing a motherboard swap and adding another hard drive.  Dell PSUs don't tend to have the best efficiency, and so it would be better to just find a cheap 400 to 600w unit that would fit in a Dell case (given that it's going in one).
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Eliot
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« Reply #4 on: March 05, 2008, 06:28:15 AM »

Well I was just worryed about not having enough amps.

As always it depands on the configuration. With an old quad-core you may have issues, otherwise you should be fine.


best,

Eliot.
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aznstriker92
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« Reply #5 on: March 06, 2008, 01:28:10 AM »

Well I have a pentium D 920, 2 gig DDR2 @ 667mhz, X600 128mb, 250HDD. I used the psu calculator thing and I won't use over 300 watts but im worried about the 22amps.
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Eliot
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« Reply #6 on: March 06, 2008, 02:56:06 AM »

Well I have a pentium D 920, 2 gig DDR2 @ 667mhz, X600 128mb, 250HDD. I used the psu calculator thing and I won't use over 300 watts but im worried about the 22amps.

22A x 12V = 264W

D920 is quite powerhungry... 95W Intel TDP -> max. ~ 130W, so you have about 130W left for the rest.


best,

Eliot
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manwe
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« Reply #7 on: March 06, 2008, 08:53:14 AM »

Well I have a pentium D 920, 2 gig DDR2 @ 667mhz, X600 128mb, 250HDD. I used the psu calculator thing and I won't use over 300 watts but im worried about the 22amps.

22A x 12V = 264W

D920 is quite powerhungry... 95W Intel TDP -> max. ~ 130W, so you have about 130W left for the rest.


best,

Eliot
Elliot it doesn't work like that , it works more likely like this
22*12*(.7-.Cool = 184-211 Watts
although I'm not pretty sure but I'm telling you it doesn't work like that just for a simple reason
I've got a 600W thoughpower which rates 4 rails 18 Amps each and by measurements it should supply
18*12*4= 864 Watts just on 12 Volts rails , lol
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Eliot
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« Reply #8 on: March 06, 2008, 12:23:46 PM »

Eliot <- 1 l - it doesn't work like that , it works more likely like this
22*12*(.7-.Cool = 184-211 Watts
although I'm not pretty sure but I'm telling you it doesn't work like that just for a simple reason
I've got a 600W thoughpower which rates 4 rails 18 Amps each and by measurements it should supply
18*12*4= 864 Watts just on 12 Volts rails , lol

4 x 18 does not work Smiley it's 18A on one rail when  max. wattage of all 12V rails does not exceeds xy W.
22x12 will work, when specified so, if 22A is peak and 18A is continous... it will not work...


best,

Eliot
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manwe
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« Reply #9 on: March 07, 2008, 06:09:59 AM »

Eliot <- 1 l - it doesn't work like that , it works more likely like this
22*12*(.7-.Cool = 184-211 Watts
although I'm not pretty sure but I'm telling you it doesn't work like that just for a simple reason
I've got a 600W thoughpower which rates 4 rails 18 Amps each and by measurements it should supply
18*12*4= 864 Watts just on 12 Volts rails , lol

4 x 18 does not work Smiley it's 18A on one rail when  max. wattage of all 12V rails does not exceeds xy W.
22x12 will work, when specified so, if 22A is peak and 18A is continous... it will not work...


best,

Eliot
so you're telling me that 18 Amps is the max load amp and that 22 Amps is continues operation Amperage Huh
my PSU didn't mention 18 Amps is the max load amperage , i really don't know , maybe it's just marketing strategy , cause even on thoughpower 750W you'll see the same sticker Smiley
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aznstriker92
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« Reply #10 on: March 07, 2008, 11:38:15 PM »

SO im lost my psu max is 264watts? wth. Its supposed to be underrated.
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Eliot
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« Reply #11 on: March 11, 2008, 06:13:55 AM »

SO im lost my psu max is 264watts? wth. Its supposed to be underrated.

Sorry for late reply, have some stuff to test  Cheesy

There are peak specs and continous specs. It depands what your PSU is specified.
Most of the time it goes like: you can do 600W, when you do 180W on 3.3+5V and 410W for the 12A rails.
So, 10W are left for +5Vusb.
The 12A rails would be rated as 22A per rail, two rails = 2x 22A = 528W... but you can do the 528W only, if your mainboard does not use more than 62W on the +3.3V & +5V rail which is of course not working. So don't get confused with the specs on your PSU. It's not that easy. Of course 12V rails also means they count CPU in.

Peak vs. Continuous:
Every PSU can sustain higher amps for a short time, mostly about 30 seconds. If this time is exceeded the PSU will shut down. Continuous means the PSU can hold the specified output always.

Your PSU is rated 264W for the 12V rail(s) only. You can make a picture of the label with the specifications on your PSU and I can tell you more about your PSU.

Here an example of the Seasonic S12II 330W:

+3.3V: 18A
+5V:    20A
combined power: +3.3V & +5V: 120W
+12V1: 17A
+12V2: 17A
combined power: 12V: 288W
-12V: 0.8A
+5Vsb: 2.5A

So, 288+120 can not work... because the PSU is rated with 330W
Also 3.3V x 18A = 59.4W, 5V x 20A = 100W, total is 159.4W does not work either.
So it can use max. 18A on 3.3V but not at the same time 20A for +5V, the maximum in this case would be 12A for +5V.
If your board/equipment is using 120W on the +3.3V & +5V you can't use 288W for 12V... I guess this can only be happen on crappy ASRock boards where no ATX 2.x power connector is used. +5Vsb rated 12.5W is used for USB devices when the computer is off, so it does not count in the active state.
Have no idea what equipment is using the -12V, but it's reserved when the computer is running.
Totally you have about 320W to use.

A harddisc is using about 0.5A for 12V and about 0.8A for 5V
A mainboard is more complicated, the voltage for the memory can be generated from 3.3V, 5V or 12V rails, this is up to the engineers, but like the CPU 12V is the best guess, because it is more efficient. 1GB stick is about 4W, overclocking is increasing it. Most chipset/onboard chips are running with either 3.3V or 5V. A board should use about 30W.

So you can do some calculations yourself Wink


best,

Eliot
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aznstriker92
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« Reply #12 on: March 15, 2008, 03:58:43 AM »

Well that was confusing but I think I get the idea thanks.
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manwe
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« Reply #13 on: March 16, 2008, 07:55:18 AM »

SO im lost my psu max is 264watts? wth. Its supposed to be underrated.

Sorry for late reply, have some stuff to test  Cheesy

There are peak specs and continous specs. It depands what your PSU is specified.
Most of the time it goes like: you can do 600W, when you do 180W on 3.3+5V and 410W for the 12A rails.
So, 10W are left for +5Vusb.
The 12A rails would be rated as 22A per rail, two rails = 2x 22A = 528W... but you can do the 528W only, if your mainboard does not use more than 62W on the +3.3V & +5V rail which is of course not working. So don't get confused with the specs on your PSU. It's not that easy. Of course 12V rails also means they count CPU in.

Peak vs. Continuous:
Every PSU can sustain higher amps for a short time, mostly about 30 seconds. If this time is exceeded the PSU will shut down. Continuous means the PSU can hold the specified output always.

Your PSU is rated 264W for the 12V rail(s) only. You can make a picture of the label with the specifications on your PSU and I can tell you more about your PSU.

Here an example of the Seasonic S12II 330W:

+3.3V: 18A
+5V:    20A
combined power: +3.3V & +5V: 120W
+12V1: 17A
+12V2: 17A
combined power: 12V: 288W
-12V: 0.8A
+5Vsb: 2.5A

So, 288+120 can not work... because the PSU is rated with 330W
Also 3.3V x 18A = 59.4W, 5V x 20A = 100W, total is 159.4W does not work either.
So it can use max. 18A on 3.3V but not at the same time 20A for +5V, the maximum in this case would be 12A for +5V.
If your board/equipment is using 120W on the +3.3V & +5V you can't use 288W for 12V... I guess this can only be happen on crappy ASRock boards where no ATX 2.x power connector is used. +5Vsb rated 12.5W is used for USB devices when the computer is off, so it does not count in the active state.
Have no idea what equipment is using the -12V, but it's reserved when the computer is running.
Totally you have about 320W to use.

A harddisc is using about 0.5A for 12V and about 0.8A for 5V
A mainboard is more complicated, the voltage for the memory can be generated from 3.3V, 5V or 12V rails, this is up to the engineers, but like the CPU 12V is the best guess, because it is more efficient. 1GB stick is about 4W, overclocking is increasing it. Most chipset/onboard chips are running with either 3.3V or 5V. A board should use about 30W.

So you can do some calculations yourself Wink


best,

Eliot
thanks for your explaination but i wonder whether my PSU can ever deliver it's nominal 4*18AMPs or not  Huh
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Eliot
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« Reply #14 on: March 19, 2008, 07:09:27 AM »

thanks for your explaination but i wonder whether my PSU can ever deliver it's nominal 4*18AMPs or not  Huh

It does not need to Smiley
A graphic cards with about 100W at load will not use all the power from the 12V rail, it is safe to assume only 80W will taken from the 12V rail and 20W come from the PCIe slot. 20W are used from the +3.3V and/or +5V rail. So max. 7A are used from the PCIe rail, plenty left for other components.


best,

Eliot.
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