| Author |
Message |
Skybuck Flying
Guest
|
 Posted:
Fri Nov 11, 2005 3:00 pm Post subject:
How much amperage do the 7800GTX and 7800GT need ? |
|
|
Hello,
On this power supply calculator it says:
http://extreme.outervision.com/index.jsp
The 7800GTX needs about 118 watts of power.
The 7800GT needs about 97 watts of power.
Somewhere else I also read
Current = Watts / Voltage.
Since these cards are supposed to be powered by a single 12v+ rail/connector
(?) this would mean the amperage is about:
118 / 12 = 9.8 amperage.
97 / 12 = 8.0 amperage.
So a power supply delivering 18A on each 12v+ rail should be enough ???
However I have seen many threads say at least 18A or even 24A...
So I am a bit confused...
How much amperage/ampere do these cards really need ??
Bye,
Skybuck. |
|
| Back to top |
|
 |
Roger Hamlett
Guest
|
| Posted:
Fri Nov 11, 2005 4:48 pm Post subject:
Re: How much amperage do the 7800GTX and 7800GT need ? |
|
|
"Skybuck Flying" <nospam@hotmail.com> wrote in message
news:dl1q3o$oai$1@news1.zwoll1.ov.home.nl...
| Quote: | Hello,
On this power supply calculator it says:
http://extreme.outervision.com/index.jsp
The 7800GTX needs about 118 watts of power.
The 7800GT needs about 97 watts of power.
Somewhere else I also read
Current = Watts / Voltage.
Since these cards are supposed to be powered by a single 12v+
rail/connector
(?) this would mean the amperage is about:
118 / 12 = 9.8 amperage.
97 / 12 = 8.0 amperage.
So a power supply delivering 18A on each 12v+ rail should be enough ???
However I have seen many threads say at least 18A or even 24A...
So I am a bit confused...
How much amperage/ampere do these cards really need ??
Bye,
Skybuck.
The problem is a question of how you 'measure' a current 'rating'. If you |
look back in time, to the old IBM supplies for the original PC-AT, these
were 'rated' at 135W, conversely many of the 'clone' supplies at the same
time, were rated at 220W, yet the IBM supplies often ran systems fine,
while the latter showed problems with poor regulation. The reason was that
the IBM 'rating' was what the supply could deliver at the connectors, with
less than 5% change in regulation, while the 'clone' suppliers were uing
10% change, and often at the supply itself. Given that a couple of rails
required regulation better than 7%, on the actual board, the IBM supply
was often giving better performance than the supposedly more powerful
'clones'. The same trend has continued since, with the manufacturers with
'good' reputations, having much more margin in their specifications, than
other units.
Now the big problem with cards, CPU's etc., is not only their 'continuous'
power consumption in heavy use (the 97W/118W figure), but the rate at
which this can change. If (for instance), the card switches from an almost
idle state, to doing a heavy rendering task, the load can jump from just a
couple of amps, to nearly 10A, in a few uSec. The question is how well a
supply can maintain regulation when there is this sudden change?. Supplies
built for heavier outputs, will tend to have larger reservoir capacitors
(slowing the rate at which the rail voltage changes), and heavier driver
components, allowing the circuit to actually cope better when there is
such a change. A good analogy, would be wooden boards on a scaffolding.
Heavier boards, not only allow bigger loads to be supported, but if a load
is suddenly dropped onto the boards, they 'spring' less, with the sudden
change. It is possible to design supplies to give better behaviour for
this type of change, but 90% of PC supplies on the market, are sold with
ratings that they can only just generate, and small margins...
Hence for good reliability, it becomes necessary to build 'margins' into
the specification, and 'overrate' supplies by perhaps 20%. Some
manufacturers do give 'real' figures, and (for instance), it is perfectly
reasonable to use a Artic Cooling 350W supply on a system that needs over
300W, while conversely, many of the 500W 'clone' supplies, can only just
about handle the same requirements...
Best Wishes |
|
| Back to top |
|
|
farmuse
Guest
|
| Posted:
Sat Nov 12, 2005 12:46 am Post subject:
Re: How much amperage do the 7800GTX and 7800GT need ? |
|
|
Skybuck Flying wrote:
| Quote: | Hello,
On this power supply calculator it says:
http://extreme.outervision.com/index.jsp
The 7800GTX needs about 118 watts of power.
The 7800GT needs about 97 watts of power.
Somewhere else I also read
Current = Watts / Voltage.
Since these cards are supposed to be powered by a single 12v+ rail/connector
(?) this would mean the amperage is about:
118 / 12 = 9.8 amperage.
97 / 12 = 8.0 amperage.
So a power supply delivering 18A on each 12v+ rail should be enough ???
However I have seen many threads say at least 18A or even 24A...
So I am a bit confused...
How much amperage/ampere do these cards really need ??
Bye,
Skybuck.
1 godzillabiggagigawatt |
|
|
| Back to top |
|
|
JEBEDIAH DUPREE
Guest
|
| Posted:
Sat Nov 12, 2005 1:15 am Post subject:
Re: How much amperage do the 7800GTX and 7800GT need ? |
|
|
farmuse wrote:
| Quote: | Skybuck Flying wrote:
Hello,
On this power supply calculator it says:
http://extreme.outervision.com/index.jsp
The 7800GTX needs about 118 watts of power.
The 7800GT needs about 97 watts of power.
Somewhere else I also read
Current = Watts / Voltage.
Since these cards are supposed to be powered by a single 12v+
rail/connector
(?) this would mean the amperage is about:
118 / 12 = 9.8 amperage.
97 / 12 = 8.0 amperage.
So a power supply delivering 18A on each 12v+ rail should be enough ???
However I have seen many threads say at least 18A or even 24A...
So I am a bit confused...
How much amperage/ampere do these cards really need ??
Bye,
Skybuck.
1 godzillabiggagigawatt
|
typical black american response |
|
| Back to top |
|
|
Jim Thompson
Guest
|
| Posted:
Sat Nov 12, 2005 7:16 am Post subject:
Re: How much amperage do the 7800GTX and 7800GT need ? |
|
|
On Sat, 12 Nov 2005 00:39:18 GMT, JEBEDIAH DUPREE <JEBBIE@DUB.com>
wrote:
| Quote: | farmuse wrote:
[snip]
1 godzillabiggagigawatt
typical black american response
|
And your response? You sound like a village idiot to me.
...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice:(480)460-2350 | |
| E-mail Address at Website Fax:(480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food. |
|
| Back to top |
|
|
Steve Carroll
Guest
|
| Posted:
Sat Nov 12, 2005 9:15 am Post subject:
Re: How much amperage do the 7800GTX and 7800GT need ? |
|
|
Skybuck Flying wrote:
| Quote: | Hello,
On this power supply calculator it says:
http://extreme.outervision.com/index.jsp
The 7800GTX needs about 118 watts of power.
The 7800GT needs about 97 watts of power.
Somewhere else I also read
Current = Watts / Voltage.
Since these cards are supposed to be powered by a single 12v+ rail/connector
(?) this would mean the amperage is about:
118 / 12 = 9.8 amperage.
97 / 12 = 8.0 amperage.
So a power supply delivering 18A on each 12v+ rail should be enough ???
However I have seen many threads say at least 18A or even 24A...
So I am a bit confused...
How much amperage/ampere do these cards really need ??
Bye,
Skybuck.
I believe that you need to read the formula more carefully. |
|
|
| Back to top |
|
|
Skybuck Flying
Guest
|
| Posted:
Sat Nov 12, 2005 2:32 pm Post subject:
Re: How much amperage do the 7800GTX and 7800GT need ? |
|
|
"Steve Carroll" <ak_hermit@hotmail.com> wrote in message
news:11nb9su56bubkbd@corp.supernews.com...
| Quote: | Skybuck Flying wrote:
Hello,
On this power supply calculator it says:
http://extreme.outervision.com/index.jsp
The 7800GTX needs about 118 watts of power.
The 7800GT needs about 97 watts of power.
Somewhere else I also read
Current = Watts / Voltage.
Since these cards are supposed to be powered by a single 12v+
rail/connector
(?) this would mean the amperage is about:
118 / 12 = 9.8 amperage.
97 / 12 = 8.0 amperage.
So a power supply delivering 18A on each 12v+ rail should be enough ???
However I have seen many threads say at least 18A or even 24A...
So I am a bit confused...
How much amperage/ampere do these cards really need ??
Bye,
Skybuck.
I believe that you need to read the formula more carefully.
|
Indeed this site uses yet another formula:
http://www.ebtx.com/mech/ampvolt.htm
Watts = Amps x Volts x Length
Bye,
Skybuck. |
|
| Back to top |
|
|
John Lewis
Guest
|
| Posted:
Sun Nov 13, 2005 12:17 am Post subject:
Re: How much amperage do the 7800GTX and 7800GT need ? |
|
|
On Fri, 11 Nov 2005 18:16:08 -0700, Jim Thompson
<To-Email-Use-The-Envelope-Icon@My-Web-Site.com> wrote:
| Quote: | On Sat, 12 Nov 2005 00:39:18 GMT, JEBEDIAH DUPREE <JEBBIE@DUB.com
wrote:
farmuse wrote:
[snip]
1 godzillabiggagigawatt
typical black american response
And your response? You sound like a village idiot to me.
...Jim Thompson
|
With that name he probably is one.
John Lewis
- Technology early-birds are flying guinea-pigs. |
|
| Back to top |
|
|
spodosaurus
Guest
|
| Posted:
Sun Nov 13, 2005 12:19 am Post subject:
Re: How much amperage do the 7800GTX and 7800GT need ? |
|
|
John Lewis wrote:
| Quote: | On Fri, 11 Nov 2005 18:16:08 -0700, Jim Thompson
To-Email-Use-The-Envelope-Icon@My-Web-Site.com> wrote:
On Sat, 12 Nov 2005 00:39:18 GMT, JEBEDIAH DUPREE <JEBBIE@DUB.com
wrote:
farmuse wrote:
[snip]
1 godzillabiggagigawatt
typical black american response
And your response? You sound like a village idiot to me.
...Jim Thompson
With that name he probably is one.
John Lewis
- Technology early-birds are flying guinea-pigs.
|
Or the governor of Florida...same difference...
--
spammage trappage: remove the underscores to reply
I'm going to die rather sooner than I'd like. I tried to protect my
neighbours from crime, and became the victim of it. Complications in
hospital following this resulted in a serious illness. I now need a bone
marrow transplant. Many people around the world are waiting for a marrow
transplant, too. Please volunteer to be a marrow donor:
http://www.abmdr.org.au/
http://www.marrow.org/ |
|
| Back to top |
|
|
Jim Thompson
Guest
|
| Posted:
Sun Nov 13, 2005 12:22 am Post subject:
Re: How much amperage do the 7800GTX and 7800GT need ? |
|
|
On Sat, 12 Nov 2005 18:17:05 GMT, john.dsl@verizon.net (John Lewis)
wrote:
| Quote: | On Fri, 11 Nov 2005 18:16:08 -0700, Jim Thompson
To-Email-Use-The-Envelope-Icon@My-Web-Site.com> wrote:
On Sat, 12 Nov 2005 00:39:18 GMT, JEBEDIAH DUPREE <JEBBIE@DUB.com
wrote:
farmuse wrote:
[snip]
1 godzillabiggagigawatt
typical black american response
And your response? You sound like a village idiot to me.
...Jim Thompson
With that name he probably is one.
John Lewis
- Technology early-birds are flying guinea-pigs.
|
Or French ?:-)
Have you heard what trouble the French are into now? Seems the
terrorists burned down the white flag factory ;-)
...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice:(480)460-2350 | |
| E-mail Address at Website Fax:(480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food. |
|
| Back to top |
|
|
Fred Abse
Guest
|
| Posted:
Sun Nov 13, 2005 1:15 am Post subject:
Re: How much amperage do the 7800GTX and 7800GT need ? |
|
|
On Sat, 12 Nov 2005 11:22:33 -0700, Jim Thompson wrote:
| Quote: | Have you heard what trouble the French are into now? Seems the
terrorists burned down the white flag factory ;-)
|
You owe me for a new coffee cup, keyboard, shirt, pair of pants and carpet :-)
--
"Electricity is of two kinds, positive and negative. The difference
is, I presume, that one comes a little more expensive, but is more
durable; the other is a cheaper thing, but the moths get into it."
(Stephen Leacock) |
|
| Back to top |
|
|
Rich, Under the Affluence
Guest
|
| Posted:
Sun Nov 13, 2005 1:15 am Post subject:
Re: How much amperage do the 7800GTX and 7800GT need ? |
|
|
On Sat, 12 Nov 2005 18:17:05 +0000, John Lewis wrote:
....
| Quote: | John Lewis
- Technology early-birds are flying guinea-pigs.
|
The early bird gets the worm, which is fine if you like worms for
breakfast. ;-)
Cheers!
Rich |
|
| Back to top |
|
|
David Maynard
Guest
|
| Posted:
Sun Nov 13, 2005 1:15 am Post subject:
Re: How much amperage do the 7800GTX and 7800GT need ? |
|
|
Jim Thompson wrote:
| Quote: | On Sat, 12 Nov 2005 18:17:05 GMT, john.dsl@verizon.net (John Lewis)
wrote:
On Fri, 11 Nov 2005 18:16:08 -0700, Jim Thompson
To-Email-Use-The-Envelope-Icon@My-Web-Site.com> wrote:
On Sat, 12 Nov 2005 00:39:18 GMT, JEBEDIAH DUPREE <JEBBIE@DUB.com
wrote:
farmuse wrote:
[snip]
1 godzillabiggagigawatt
typical black american response
And your response? You sound like a village idiot to me.
...Jim Thompson
With that name he probably is one.
John Lewis
- Technology early-birds are flying guinea-pigs.
Or French ?:-)
Have you heard what trouble the French are into now? Seems the
terrorists burned down the white flag factory ;-)
...Jim Thompson
|
Makes on wonder who surrenders first when both sides are French. |
|
| Back to top |
|
|
bowgus
Guest
|
| Posted:
Tue Nov 15, 2005 1:15 am Post subject:
Re: How much amperage do the 7800GTX and 7800GT need ? |
|
|
Or just look here ... http://www.slizone.com/page/home.html Hmm,
wellwouldyalookathat ... there's my 600w seasonic on the recommended PS list
:-)
|
|
| Back to top |
|
|
|
|
|
|
FAQ
Memberlist
Register
Profile
Log in to check your private messages
Log in