Why so much emphasis on big wattage?

Dman877

Platinum Member
Jan 15, 2004
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300 watts is more then enough

"Our own experience shows idle AC power consumption of 60~90W, and about 110~130W at 100% CPU utilization in several fairly representative mid-line test systems. Given the typical 65~70% effiiciency of a PSU, the DC power delivered is 40~60W at idle and 80~90W maximum. In other words, the amount of power actually required by typical desktop systems is about 30% of the capacity of the typical 300W power supply."

Good article from silentpcreview. This explains why the 200 watt psu in my shuttle xpc can handle an xp 2400 and gf4 with no problems :).

If you believe some of the posts on here, you need 400 watts minimum to run a gameboy :p.
 

mechBgon

Super Moderator<br>Elite Member
Oct 31, 1999
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Originally posted by: Dman877
300 watts is more then enough

"Our own experience shows idle AC power consumption of 60~90W, and about 110~130W at 100% CPU utilization in several fairly representative mid-line test systems. Given the typical 65~70% effiiciency of a PSU, the DC power delivered is 40~60W at idle and 80~90W maximum. In other words, the amount of power actually required by typical desktop systems is about 30% of the capacity of the typical 300W power supply."

Good article from silentpcreview. This explains why the 200 watt psu in my shuttle xpc can handle an xp 2400 and gf4 with no problems :).

If you believe some of the posts on here, you need 400 watts minimum to run a gameboy :p.
I skimmed the article and found zero explaination of their statement. Any idea what tests they did?
 

Dman877

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It's a review site (like this one) so you sort of have to take their word for it that their measurements are accurate. They measure AC power consumption at the wall and extrapulate based on power efficiency ratings as to the DC output. This article wasn't specifically about power use though, the discussion was sort of incedent but I found it interesting anyway. I always wondered why everyone on these boards recommends massive wattage figures whenever someone is having a problem :).
 

mechBgon

Super Moderator<br>Elite Member
Oct 31, 1999
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Originally posted by: Dman877
It's a review site (like this one) so you sort of have to take their word for it that their measurements are accurate.
No I don't. :) I will give their position serious consideration if/when they explain what they did to test. Knowing the actual thermal output of some of today's high-end components (50W+ for video cards, 60-100W for CPUs), I have to wonder if their tests were using the video card to any significant extent, for starters.

That said, you'll find that the first thing people focus on here is not lots of wattage, it's quality wattage. If you haven't noticed that focus, then I'm rather surprised. People post that they are having instability problems, and say that they have a 400W or 450W or 500W PSU or whatever, and the experienced troubleshooting helper-outers will still pry on the person for the brand of the 400/450/500W unit to determine if it's JUNK or something respectable. :D
 

Texun

Platinum Member
Oct 21, 2001
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I have a theory that I can't prove, but hey...

My thoughts on the PS craze is this: For starters, many power supplies are relatively cheap and horribly inefficient. Manufactures compensate for the inefficiency by turning up the wattage ratings. In general, its a sloppy solution to the problem. It's not that you really need a high watt rating, but many of the cheaper PSU manufactures build PSUs that allow the load to be pulled from one rail when the current draw on another rail increases, usually resulting in a failure of some kind. It is this poor design ( and some marketing hype) that drives them to turn out even more inefficient PSUs to compensate for this weakness.

A more efficient (well made) PSU will have the power to meet the demand without stealing it from another rail. Antec is designed this way. I read something about this years ago but I can't remember where I saw it.

As far as 300W being more than enough, it would depend largely on what it was being used for. A high end system with a strong cpu, video card, etc would stress even a good 300W PSU. It *may* run fine for a while but you can bet it would be running in the red.

Others may be able to give a better explanation that I did. Hey... I tried. I need a break. :beer:
 

Dman877

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Jan 15, 2004
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Originally posted by: Texun
I have a theory that I can't prove, but hey...

My thoughts on the PS craze is this: For starters, many power supplies are relatively cheap and horribly inefficient. Manufactures compensate for the inefficiency by turning up the wattage ratings. In general, its a sloppy solution to the problem. It's not that you really need a high watt rating, but many of the cheaper PSU manufactures build PSUs that allow the load to be pulled from one rail when the current draw on another rail increases, usually resulting in a failure of some kind. It is this poor design ( and some marketing hype) that drives them to turn out even more inefficient PSUs to compensate for this weakness.

A more efficient (well made) PSU will have the power to meet the demand without stealing it from another rail. Antec is designed this way. I read something about this years ago but I can't remember where I saw it.

As far as 300W being more than enough, it would depend largely on what it was being used for. A high end system with a strong cpu, video card, etc would stress even a good 300W PSU. It *may* run fine for a while but you can bet it would be running in the red.

How many times have you seen someone on here say "stability problems? what you need is a high quality 300 watt psu?" I think a lot of it is how we got caught up by the marketing involved (read page 2 of the article for specifics).

Others may be able to give a better explanation that I did. Hey... I tried. I need a break. :beer:

That's pretty much exactly what they said in their article. Also, to mechbgon, I'm not impuning the "experienced troubleshooters" on these boards, just pointing out how many posts I see about 400 watts this and 550 watts that.

 

Peter D

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Oct 28, 2002
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Originally posted by: Dman877
Why so much emphasis on big wattage?

'Cause average people choose quantity over quality when it comes to computers. Thats true for stuff like PSU's (''More Watts = Bettar!"), CPU's ("This Celeron 2.6GHz must be better than this 1.8GHz Barton!"), RAM, etc :p That said, I got a 460W just for headroom for future additions, but its a quality Enermax, so :p
 

Dman877

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Jan 15, 2004
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Originally posted by: Vegetto
Originally posted by: Dman877
Why so much emphasis on big wattage?

'Cause average people choose quantity over quality when it comes to computers. Thats true for stuff like PSU's (''More Watts = Bettar!"), CPU's ("This Celeron 2.6GHz must be better than this 1.8GHz Barton!"), RAM, etc :p That said, I got a 460W just for headroom for future additions, but its a quality Enermax, so :p


Gotcha. So those pc speakers with 2000000 watts pmpo that cost 15$ must be way better then the Klipsch 5.1 at a measily 500 watts woohoo :). Yeah I guess it's not a big deal, a quality 400 watt psu is only like 50$ anyway.
 

Texun

Platinum Member
Oct 21, 2001
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Originally posted by: Vegetto
Originally posted by: Dman877
Why so much emphasis on big wattage?

'Cause average people choose quantity over quality when it comes to computers. Thats true for stuff like PSU's (''More Watts = Bettar!"), CPU's ("This Celeron 2.6GHz must be better than this 1.8GHz Barton!"), RAM, etc :p That said, I got a 460W just for headroom for future additions, but its a quality Enermax, so :p

Yep.. It has as much to do with marketing than anything else. The part that burns me up is that instead of making a stronger brick they pump it full of air to make it look bigger. Nothing sells a product better than smoke and mirrors.

Manufactures like this one cater to the uninformed. 500W A-Power - only $18.89!.

 

beatle

Diamond Member
Apr 2, 2001
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I don't understand why people think they need 400+ QUALITY PSUs. Dual cpus and several (5+) hard drives, nobody needs that much power in reserve. See the duallie rig in my sig... it's plenty stable with a 5+ year 300w PSU.
 

Tab

Lifer
Sep 15, 2002
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The bigger the powersuppply, the bigger the penis. :)

My thoughts on the PS craze is this: For starters, many power supplies are relatively cheap and horribly inefficient. Manufactures compensate for the inefficiency by turning up the wattage ratings. In general, its a sloppy solution to the problem. It's not that you really need a high watt rating, but many of the cheaper PSU manufactures build PSUs that allow the load to be pulled from one rail when the current draw on another rail increases, usually resulting in a failure of some kind. It is this poor design ( and some marketing hype) that drives them to turn out even more inefficient PSUs to compensate for this weakness.

Do you have any more information of this? I'd like to know how well have all these crappy 500-Watts and the such. In reality I just want to pwn my friends telling I spent my money a nice antec :p
 

lazybum131

Senior member
Apr 4, 2003
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Here's an older thread at SilentPCReview with more details on how the wattage test can be performed, and some numbers too: Question about how to use Kill-A-Watt Device

If you just want numbers, scroll down halfway on the first page and read the posts for users 'wumpus' and 'silentbob'. Note the wattage numbers are for AC, not DC so they don't take into account for efficiency of the PSU.

For the lazy:

silentbob's dual Barton XP2500's, overclocked to 15 * 150 FSB @ 1.75 Vcore, with GF4 Ti4600 uses "249 watts, when idling in the BIOS. At full load, as described above, it has wattage spikes up to 357 watts. At full load, running all tests above, except the 3DMark2003 test, the system uses 320 watts."

And here's how he got his system to full load:
I did idle and full load tests. For idle testing, I just booted up into the BIOS and watched the Kill-A-Watt. It doesn't fluctuate much, when the system is booted to BIOS. For full load testing, I used several programs, together, to stress every component in the system. First, I started up to instances of Prime95. Since I have 2 CPU's, I must run two instances of this program to max out both CPU's. Second, I started Passmark's BurnInTest, and ran it. It was set to stress test the CPU Math, CPU MMX, RAM, both Optical drives (does reads of the discs in the drives), both hard drives, the floppy drive (reads and writes to floppy disk), Sounds, and Network. Third, I fired up 3DMark2003 and ran it through. The second test and first 15 seconds of the third test seem to be the most stressful (in wattage), on my video card. I would let 3DMark2003 run through, let BurnInTest go through its test (the evaluation is limited to a 15 minute run), and let Prime95 run. If all went through without errors, I recorded the numbers.

So I doubt many ppl run a 'typical system' consisting of dual overclocked CPUs running all those programs at once stressing so many components. And even if they do, this system spiked at 357 watts of AC power, which is about 232 - 286 watts of DC power assuming PSU efficiency between 65-80%.
 

Dman877

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Jan 15, 2004
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Originally posted by: beatle
I don't understand why people think they need 400+ QUALITY PSUs. Dual cpus and several (5+) hard drives, nobody needs that much power in reserve. See the duallie rig in my sig... it's plenty stable with a 5+ year 300w PSU.

Good point but TBH, you are using cpu's from 5 years ago :).
 

Jhhnn

IN MEMORIAM
Nov 11, 1999
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The first thing that any novice computer afficianado needs to learn is that there is absolutely no truth in advertising for PSU's- zero, zip, zilch, nada, nyet. I'll take a heavyweight 300w Fortron over a flyweight 500w no-name pos any day. The Fortron will put out max rated power for years, whereas the other will put out 500w for a few hours, at best... The Fortron has a solid reserve of short duration peak power, as well, whereas the cheapo essentially has none...

Nobody can build a quality psu that sells for less than ~$.90/watt, nobody. It's just that simple. And that price per watt goes up as the power rating goes up, because the manufacturer is losing part of the economy of scale gained from making millions of popular wattage units....

One of the things folks don't realize is that current draw is at maximum during boot- spinning up the drives and the initial power surge to load the chokes and capacitors is quite large, and instantaneous. It takes a lot of peak power to boot a system with multiple drives, fans, high end vidcard, etc, but not a lot to keep it running.

Add the fact that the overclocking craze creates systems that are very sensitive to low voltage at the processor. Small sags that a stock clocked system will brush off spell boot failure in heavily overclocked systems. So rabid overclockers need more reserve power, peak power, than ordinary computer geeks...

Sometimes overclocking makes sense, particularly when the chip makers enter the phase of manufacturing where they downgrade chips to lower speeds for marketing reasons. It doesn't make sense, however, in the context of needing a $70 psu upgrade to to overclock to speeds you could have had with a simple $30 cpu upgrade...
 

Zepper

Elite Member
May 1, 2001
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Your SFF PC uses the P4 Aux connector (12V rail) to power the CPU - that's why it can run on 200W - note that the +12V rating on that PSU is probably quite a bit higher than you'll find in a typical 200W PSU (around 7 or 8A). Try to run an ECS K7S5A mobo on less than a good quality 350 Watter or so... fageddabaouddit! Cheap mobos need the P4 Aux connector more than the expensive mobos (because people that buy cheap mobos sould be able to use cheap PSUs with them, shouldn't they???) but that's generally not where you find them.
. Uless you are a max OCer and use an Amp sucking vid card (ATI 9800, et al.) 350W or less w/ 13A or more on the +12V should do fine. I have seven drives (and the 3 SCSI HDs are set to spin constantly) in my machine and it was running fine on a 250W Sparkle until I got my new case and I don't think its temp controlled fan ever cranked up to full speed.
. Want big (fill in the blank: car, psu, cpu house, etc.) to compensate for small PP. NOT Big = Big - that's wishful thinking...
.bh.
 

mechBgon

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Oct 31, 1999
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Another factor that I think is getting glossed over here is that it is very shallow to simply measure the total wattage of the components and declare that "it's less than 300W, so a 300W PSU is therefore sufficient." It's on a per-rail basis that counts, as the AMD Builder's Guide tries to convey. A system with extreme 3.3V + 5V demands, like the K7S5A that powers the CPU from the 5V line, might be drawing enough 3.3V + 5V power that you need a 350W+ unit to cover it, whereas the same hardware with a Shuttle AN35N Ultra might be content with your SFF 200W unit due to the different loading of the voltage rails (AN35N Ultra uses the ATX12V connector and I presume it powers the CPU from that line, which is typically generated independently of the 3.3V + 5V branch).

I was a career bicycle mechanic for more than 10 years, and built thousands of pairs of custom wheels. I can build very light "race-weight" wheels, and do a nice job on them so that a 200-pound rider or even a tandem team can use them... for a while. But I always preferred to overbuild, rather than riding the fine line of "just enough strength." The rider will remember that the wheels held up year after year, a lot longer than he/she will remember that they were 20 grams lighter :) Sure, I've had some crazy-light wheels myself (Zipp440 all-carbon tubulars with Zipp carbon hubs light enough for ya? Let me tell you why I really created and use the Cheetah avatar... :evil: ) but the wheels that have lasted for the long haul... well, let's see, the ones on my Cannondale full-tourer were built in 1994 if I remember correctly.

Moral of the story: get back to me in three to four years, and we'll compare notes on what's held up better for the long haul, the "just-enough" units or the "overkill" units.
 

Dman877

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Jan 15, 2004
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If a typical system uses 150 - 200 watts, a 300 watt psu is "overbuilt" wouldn't you say? A 650 watt psu is just more "overbuilt."
 

mechBgon

Super Moderator<br>Elite Member
Oct 31, 1999
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Originally posted by: Dman877
If a typical system uses 150 - 200 watts, a 300 watt psu is "overbuilt" wouldn't you say? A 650 watt psu is just more "overbuilt."
Did you not read what I just posted? ;) Tell me the per-rail load... heck, never mind. I see you're on one of those crusades that people sometimes get absorbed in, so don't let me get in the way :) I build systems for my employer that are expected to have a 5-year service life before retirement, and I don't care what they could be run on, they are going to have the "towing package" power supply as long as I'm the one spec'ing them (and answering the phone when they have problems). Time will prove where wisdom lies.
 

Dman877

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Jan 15, 2004
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So it's important to understand the specs of a psu and configure systems according to power needs (ie your ECS mobo example). That still doesn't explain why 500 watts is needed...

It sounds like you're the one on a crusade to justify your power "requirements."
 

smahoney

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Apr 8, 2003
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I looked for Quality and Features - I have never had a problem with an Antec, yet have burned more than a few others to a crisp. Sure your Dell, IBM or HP corporate desktop only comes with a 200~250 Watt unit as a basic supply, but they are all quality units that are highly efficient. If you are building a custom system and are overclocking with some extreme components you can expect to draw quite a bit more wattage from your PSU that needs to be STABLE. I could have gone with a 350W but went for a 480 since it was only a few dollars more and I didn't want to even think about not having enough juice. I also could have gone with a 430 but I wanted the blue leds ;).

I just think if you are going to be overclocking your CPU by 25% and are overvolting your ram and running large SATA arrays with faster drives - why take a cahnce on a cheapo or underpowered PSU.