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electricity and psu

geff_r

geff_r

geff_r

Permabanned
Joined
31 Jan 2007
Posts
459
I was wondering why the min psu requirements are now around
the 500 watt mark seeing as tft use less power the core 2 duo uses less power
it can't purely be the graphics cards can it?Am i missing something?
has anyone even tested a core 2 duo with say a 350 watt power supply
and 16x pci express?everything seems to be using less power yet the power supply requirements seem to be going up and up.I've done some calculations
and this means your average pci express card uses 200 watts of power?
edit monitor runs off it's own power doh ! but what about the cpu using less volts and power?
 
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I guess it depends on what you intend to do with your PC. A 8800GTX comes with recommended 600W PSU. Put this together with an OC CPU, several HDDs, a few DVD's, a case full with "optional" fans, 2 Gb (now more people get 4 Gb) RAM and you will be surprised how much juice you need to have everything running smoothly. Here I do not mention SLI or Cross Fire enthusiasts.

You could easily justify a 1000 W PSU :) .

I have always wondered why the sites that offer power PC calculators usually overestimate the power needed.
 
Hmm well core 2 duo 1 hdd 1 dvd 1 sound card 1 graphics no usb 2 fans = 400 watts+ on most calculators.
we will soon find out as i intend running that on my enermax 35o watt soonish.
It must be that the core 2 duos need twice as much as say a barton and pci express need twice as much as agp then.
 
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Dunno, just did a quickie on extreme psu calc (alebit its only good for a general wattage amount and dosen't factor how many amps are needed)

X6800
8800GTX
2 sticks DDR2
Sound blaster
DVD-RW
1 SATA
2 120mm
1 PCI card

327W

do remember that on these calculators the dual core cpus are counted as single and not dual cpu configuration.
 
psu calculators are all bollards.

geff_r said:
I was wondering why the min psu requirements are now around
the 500 watt mark seeing as tft use less power the core 2 duo uses less power
it can't purely be the graphics cards can it?Am i missing something?
has anyone even tested a core 2 duo with say a 350 watt power supply
and 16x pci express?everything seems to be using less power yet the power supply requirements seem to be going up and up.I've done some calculations
and this means your average pci express card uses 200 watts of power?
edit monitor runs off it's own power doh ! but what about the cpu using less volts and power?
Click to expand...

core2's use less than what? you only know that they are decreasing the thermal output, not the input required. whilst that is lowering transistor for transistor compared to older, large processes, they still require a lot of power. The fact that the complexity of the chips is ever increasing only serves to increase that power requirement.

It's the same argument with graphics cards. Many people think smaller process = less power and less heat. wrong, it doesnt mean that at all. Purely from the manufacturer's point of view it means they are cheaper to produce and they can stuff more transistors per core in.

That's the real story. running on a smaller process will mean that, generally, a gpu would use less power than it would on a larger process. but when they are doubling the transistor count in each new part, that pretty much cancels out those benefits and in fact, it usually means more power is required even if less heat is produced.

it would be interesting to see what a shrink to 65nm would do for the g80. 681 million transistors on a 90nm process is just amazing, but they do require a fair amount of juice. They put out an equal amount of heat as well.
 
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Well to me if you want 6300 2 x sata a soundblaster 8800gts
1 x dvdrw 2 case fans 2 sticks of ddr2 6400 and i'd say that's about the average users pc you will not need much over a 400w power supply.
I guess buying a power supply is all about future proofing too in a way.
My 4 year old enermax 350 watt could probably run that setup just about.
I'd just like a much more accurate calculator no point shelling out for a high end psu if you're not going to even need one is my view.This is only because i am on a tight budget for my upgrade of course.So i think i'll get the corsair 520 watt.But i'd rather save £30 and get something which is just as ample for that setup though.
There are a lot of 400watt sli compliant power supplys is the confusing thing.
yes i did think that lower vcore meant less power consumption i learn again.
 
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james.miller said:
core2's use less than what? you only know that they are decreasing the thermal output, not the input required.
Click to expand...

All the power that a CPU uses is output as heat.

Jokester
 
a lot of these power estimates are just nonsence though.

My system is as follows
E6700 @ 3Ghz
Geforce 7900GTO
2GB Corsair C3 ram
2x Seagate 7200.10 (320gig)
SoundBlaster X-Fi
4 Fans (Glowing LED ones)
DVD RW
Zip Drive
Floppy Drive!
Fan Controller

Power use on standby 9Watts
Power use in windows Idle 120W (Speedstep disabled)
Power use in windows 2xPrime95 cpu 100% load 175W
Power use in Oblivion (1cpu fully loaded 1 cpu lightly loaded, GPU heavily loaded) 195W

All power measurements made with a plugin power monitor.

My P4 3.2Ghz Northwood with Geforce 6800GT used 40% more power (both at idle, and full load)
 
james.miller said:
psu calculators are all bollards.



core2's use less than what? you only know that they are decreasing the thermal output, not the input required. whilst that is lowering transistor for transistor compared to older, large processes, they still require a lot of power. The fact that the complexity of the chips is ever increasing only serves to increase that power requirement.

It's the same argument with graphics cards. Many people think smaller process = less power and less heat. wrong, it doesnt mean that at all. Purely from the manufacturer's point of view it means they are cheaper to produce and they can stuff more transistors per core in.

That's the real story. running on a smaller process will mean that, generally, a gpu would use less power than it would on a larger process. but when they are doubling the transistor count in each new part, that pretty much cancels out those benefits and in fact, it usually means more power is required even if less heat is produced.

it would be interesting to see what a shrink to 65nm would do for the g80. 681 million transistors on a 90nm process is just amazing, but they do require a fair amount of juice. They put out an equal amount of heat as well.
Click to expand...


As well as Corasik's findings, heres another one for ya, have a mess-about rig with an DS3 board and a few hdds that would not run stable with a FSP 300w psu i tried just for kicks a few months ago, the system basically refused to load windows many times or as soon as the cpu was put under load it rebooted, this was nothing to do with temps etc.. it was fine with an Enermax liberty 400w psu. This was with an 820 at stock speed, recently put an E6400 at 3.2Ghz in it and tried the 300w psu just for kicks again, system runs a-ok and primed for 50+ hours whereas with the 820 it would reboot in less than a minute, nothing but the cpu was changed and even the FSB was more and VDIMM higher as the Core 2 was actually overclocked as opposed to the 820, this was at stock core 2 volts. So while you may have some valid points theres definetly proof out there that core 2 uses less juice than Netburst.
 
I can confirm the power usages.

E4300 @ 3.3Ghz
Abit 650
1 x HDD
1 x DVD
2GB PC6400
4x 120mm fan ~ 1200rpm
7800GTX 256MB

Usage approx 200w with Orthos
Max usage seen approx 260W during gaming.

The most important part of the PSU is the +12v output. Modern systems take most of the power for the CPU and GPU from the +12v supply so this needs to be robust. Many older 300/350w supplies only have 8-12 A (96-144w) on the 12v rail and it's just not enough.

AD
 
Heavy graphics and worst case scenarios i guess.

Stated power output means nothing. I would take 300W with rail regulation of 50mVp-p 10KHz sine over typical consumer 1KW supplies any day...
 
I was wondering why the min psu requirements are now around
the 500 watt mark seeing as tft use less power the core 2 duo uses less power
it can't purely be the graphics cards can it?Am i missing something?
Click to expand...
It has already been said above but there are two important factors, one is very few power supplies can actually sustain the load you might assume, i.e. a 1000 Watt PSU is NOT 1000 Watt of sustained power output (and even if it can, it isn't advisable to be using a PSU close to the max capacity cos it A: won't last and B: will be unstable), infact if you make it do that (on the average PSU) it'll blow (they are also not 100% efficient and you can't rely on the stated wattage, since it may only be peak or rated inaccurately, like full power and MTBF only at 25C, who has a PSU that runs at 25C?).

Second (again said above already :p ), the distribution of power on the rails is not necessarily where you want it, modern PCs draw most of their juice from the +12v rails (particularly graphics cards, which are the biggest culprit in most of our PCs) and older/crappier PSUs can't deal with this (having either poor stability/performance or inappropriately distributed load). There is a vast difference between a decent quality 400 Watt PSU and some generic tat that came with a £15 case/PSU bundle (but manufacturer estimates rarely make any distinction).
 
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As decto says, these days pretty much assume 99% of a PC's power requirements are being drawn from the 12V rail, so as my system 'averages' out at 195W, there are natually going to be some spikes that are so short the plugin power monitor doesnt register them.

195W drawn from the 12V rail is 16.25amps. My previous 400W Zalman PSU only had a 18Amp 12V rail if I remember correctly, so while that may be enough for the systems average load, it may struggle if the system needs any 'extra' power.

On the other hand, I have an old (but still going strong) Enermax PSU, which is only rated at 350W, but has a 26Amp 12V rail, it's never failed me on any system so far. (I've never built an SLI system, so 26A is pretty much all I needed).

Have to admit, Im running a Seasonic S12 500W supply. But the reason for this is A) 80% efficiency, its one of the most power efficient PSU's around, B) its quiet. Infact the seasonic draws about 15W less than the Enermax when powering my Core2 system.
 
Ive just bought one of them from an auction site. Gotta wait until it arrives till i can find out how money it costs to run it . . .
 
Justintime said:
Got 2 somewhere, haven't got about to actually trying em, must find them first i guess! :D
Click to expand...

Apparnty my computer that on about 16 hours a day, with my ups that uses 45-50watts 24-7. All together my computer setup uses about £150-£180 a year. :eek:
 
The power rating of a PSU doesnt mean anything. Stable rails and a good, stable, high, current do. I'd have my 350W Enermax over a 1kW Qtec anyday.
 
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