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FlipSid309

18 Posts

14224

April 7th, 2008 16:00

E520 8800GT

I've got a dell e520, had it since last may or so. I want to put a new card in it.

This is the one i want: http://www.newegg.com/Product/Product.aspx?Item=N82E16814130318

 

I only have the stock 305W PSU in my computer still. I've read places that people have been able to use this card without upgrading their PSU. If thats the case where do i plug in the cords to I did not see any available spots to plug it in. Will the cord that comes with this video card work or do I need another one?

 

ty_ger

812 Posts

April 7th, 2008 16:00

I would not run that card on your 305W power supply.  350W watt is pushing it, but has been done.

ae38cb5bb8b0410

1.1K Posts

April 7th, 2008 17:00

@ty_ger wrote:
I would not run that card on your 305W power supply.  350W watt is pushing it, but has been done.

I would not do it myself, but what do you mean 350w is "pushing it"?

305w psu = 22amps

350w psu = 28amps

375w psu = 30amps

 

8800GT can run with 22amps, but like I said I wouldn't myself.

http://www.evga.com/products/moreInfo.asp?pn=512-P3-N802-AR

 

 

Requirements 

 Minimum of a 400 Watt power supply.
(Minimum recommended power supply with +12 Volt current rating of 22 Amp Amps.)
Minimum 450 Watt for SLI mode system.
(Minimum recommended power supply with +12 Volt current rating of 24 Amp Amps.)

An available 6 pin PCI-E power connector (hard drive power dongle to PCI-E 6 pin adapter included with card)

 

 

ty_ger

812 Posts

April 7th, 2008 18:00

Hmm...

 

Sure a 350W power supply theoretically could have 29A available on the 12V rail, but in reality some of that total rated wattage is going to 3.3v and 5v rail and other 12V loads.  Typically this question comes up with an Inspiron 530 which would have a quadcore processor to have the 350W power supply.

 

Lets just play with some numbers...

First of all the Q6600 requires up to 105W to operate at full load.

That drops us down to 245W total available (350W-102W).

Lets say you require an additional 1A on the 5V rail for hard drive/cr-rom drive and .5A on the 3.3V rail.

That would mean the 5v and 3.3v load is putting an additional 6.65W load on the power supply ((5Vx1A)+(3.3Vx.5A))

245W-6.65W= 238.35W left

238.35W on 12V rail is a bit less than 20A (238.35W/12V) available to the video card in this situation.

 

Now, you have to factor in that the power supply is only maybe 75% efficient due to some of that energy going into the form of heat; so you don't have an actual 350W to begin with... Also, the numbers on the 5V and 3.3V amperage load I used are VERY conservative.

 

Is this "350W psu = 28A[available on the 12v bus]" a real spec written somewhere?

Message Edited by ty_ger on 04-09-2008 02:56 PM

ae38cb5bb8b0410

1.1K Posts

April 7th, 2008 19:00

@ty_ger wrote:

Hmm...

 

Sure a 350W power supply theoretically could have 29A available on the 12V rail, but in reality some of that total rated wattage is going to 3.3v and 5v rail and other 12V loads.  Typically this question comes up with an Inspiron 530 which would have a quadcore processor to have the 350W power supply.

 

Lets just play with some numbers...

First of all the Q6600 requires up to 105W to operate at full load.

That drops us down to 245W total available (350W-102W).

Lets say you require an additional 1A on the 5V rail for hard drive/cr-rom drive and .5A on the 3.3V rail.

That would mean the 5v and 3.3v load is putting an additional 6.65W load on the power supply ((5Vx1A)+(3.3Vx.5A))

245W-6.65W= 238.35W left

238.35W on 12V rail is a bit less than 20A (238.35W/12V) available to the video card in this situation.

 

Now, you have to factor in that the power supply is only maybe 75% efficient due to some of that energy going into the form of heat; so you don't have an actual 350W to begin with...

 

Is this "350W psu = 28A[available on the 12v bus]" a real spec written somewhere?

"Is this "350W psu = 28A[available on the 12v bus]" a real spec written somewhere?"

 

I deal in facts, with documentation.

I never had a 350w psu, I only rely by what other forum members who had the 350w psu.

I did have the 305w that came with my system (E521) and it does have 22amps.

Look for youself:

http://i239.photobucket.com/albums/ff305/kpo6969/0d5032-2.jpg

 

Now lets deal with some real math:

@2 12v rails @ 18A each

264w maximum combined wattage on the combined 12v rails

264 divided by 12 = 22amps

 

You can play with numbers, that is your right.

FlipSid309

18 Posts

April 9th, 2008 17:00

i brought my computer into a computer store to search for a PSU for it and they didnt have any that fit, can you guys tell me of a couple PSU's that have been known to fit inside the E520 case i would prolly be looking from 500 to 600

ty_ger

812 Posts

April 9th, 2008 18:00

Well, I have to disagree with your math too.

 

All these different voltage buses ("rails" ) run off the same multitap transformer.  The transformer is rated for 305W output.  This means that if you load up one bus, there is less available on another.  You can't calculate the amperage available on a certain bus without considering all the other loads on the other buses.

 

If you loaded up all those buses to their max (22A@5V, 2@5V, 18A@12V, 17A@3.3V, 18A@12V) you would see that you are putting a 608.1W load on the transformer.  If that was possible, don't you think that the power supply would be rated at 608.1W?

 

EDIT: Space between " and ) in ("rails" ) so there would be no ("rails")

 

@kpo127 wrote:

 

Now lets deal with some real math:

@2 12v rails @ 18A each

264w maximum combined wattage on the combined 12v rails

264 divided by 12 = 22amps

You must be using some power factors in the above calculations... Otherwise, how did you come up with 264W total?
(2*(12V*18A))=432W
432W = 305.4W RMS, 274.8W AVG
Message Edited by ty_ger on 04-09-2008 03:04 PM

FlipSid309

18 Posts

April 9th, 2008 20:00

lol, can anyone answer my question

 

does anyone have a E520 or E521 that put a new psu in, if so can you give me a link to it

ae38cb5bb8b0410

1.1K Posts

April 9th, 2008 22:00

@ty_ger wrote:

Well, I have to disagree with your math too.

 

All these different voltage buses ("rails" ) run off the same multitap transformer.  The transformer is rated for 305W output.  This means that if you load up one bus, there is less available on another.  You can't calculate the amperage available on a certain bus without considering all the other loads on the other buses.

 

If you loaded up all those buses to their max (22A@5V, 2@5V, 18A@12V, 17A@3.3V, 18A@12V) you would see that you are putting a 608.1W load on the transformer.  If that was possible, don't you think that the power supply would be rated at 608.1W?

 

EDIT: Space between " and ) in ("rails" ) so there would be no ("rails")

 

@kpo127 wrote:

 

Now lets deal with some real math:

@2 12v rails @ 18A each

264w maximum combined wattage on the combined 12v rails

264 divided by 12 = 22amps

You must be using some power factors in the above calculations... Otherwise, how did you come up with 264W total?
(2*(12V*18A))=432W
432W = 305.4W RMS, 274.8W AVG
Message Edited by ty_ger on 04-09-2008 03:04 PM
"You must be using some power factors in the above calculations... Otherwise, how did you come up with 264W total?"
Try reading the label of the psu, link is posted in message #5
Message Edited by kpo127 on 04-09-2008 07:33 PM

FlipSid309

18 Posts

April 9th, 2008 22:00

you very much, anyone have a 600w that fits? I'm prolly going to lean towards 500-600 range so i dont have to mess with it in the future

ae38cb5bb8b0410

1.1K Posts

April 9th, 2008 22:00

@FlipSid309 wrote:

lol, can anyone answer my question

 

does anyone have a E520 or E521 that put a new psu in, if so can you give me a link to it

This is what I have in mine (E521)

ty_ger

812 Posts

April 9th, 2008 23:00

@kpo127 wrote:
Try reading the label of the psu, link is posted in message #5
I read it and am reading it right now...
I missed the small print.
Ok,
max combined power on 3.3V and 5V is 150W
max combined power on 12V is 264W
That adds up to 414W; and your PSU is rated at 305W.
This is another example of why you have to take into account what is on the other buses.  You cannot use all 264W on the 12v bus if you are loaded up to 150W on the 5v and 3.3v bus.... and that is why the 530 w/ quadcore has a higher rated PSU (350W) because the Q6600 uses 105W peak while the non-quadcore 530 has a 305W PSU because the Exxxx line uses around 60W peak.

ae38cb5bb8b0410

1.1K Posts

April 10th, 2008 02:00

Whatever

blah..blah..blah

 

I stated what the 305, 350, and 375w psu  12v amperage amounts were.

Believe it or not, I don't really care.

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