Why do people buy PSUs that are over 700W?

[Andaho]

i don't think that's quite right. A power SUpply only supplies the power that is requested of it. So if you ran a Celeron on it, with just one hard drive and onboard graphics, it would use a lot less power than a meaty rig. The psu would only proved what was requested of it.

ie they dont use their maximum all the time

Because a general PC is idle 99% of the time* (like now while I'm writing this), I think it sound good to buy a PSU that will have max efficiancy at the PCs watt rating when idle (which does fit in with how PSUs are manufactured, with the max efficancy being around 40-50% load).

*Do you think my guess at 99% of the time is unrealistic? I mean, when you tell the PC to do soemthing, it does it pretty much instantly, and then waits around for you to tell it to do something else.

[Andaho]

But you need to have a PSU that can cope with max power draw. What if you get to a point in a game (for instance) where everything is being stressed and your 500Watt supply can't cope? Your PC crashes. If you had a 750Watt supply, there would have been njo problem.

You need to take the maximum usage into account, ven if it only occurs very rarely.

You can compair this to bridges. A bridge might only experience winds of up to 50mph for 99.999% of the time, but it still need to be able to handle that 0.001% when the winds hit 100mph.

Yes, I understand all that, and very well put I do like the analogys But as I said earlier, the reason that made me start this thread, was seeing threads where people have said "I have this system, what PSU will I need?" and for their system, under max load, it would probably be around 350W, but people are advising them to spend £80 on 500-600W PSUs (usually the corsair 520W or 620W).

[Funkstar]

Generally everyone on here will recomend the higher end components. Thats what happend when you ask a bunch of geeks

Part of their argument with recomending Corsair will be that they are very well built and very reliable. The smallest PSU they do is 450W.

I do totally understand what you are getting at though

[Andaho]

I've read tons of reviews on PSUs over the last few weeks, and with the low power reviews, they say how happy they are with how it can handle such a powerful system, and how it could even handle more. With reviews for the powerful PSUs, I've seen a few reviews where they add several 100W light bulbs to an already top-of-the-range PC to see where the voltages will start dropping, and where the PC will refuse to power up.

Isn't that just prooving that the PSU has waaaaay too much power?

[Andaho]

Generally everyone on here will recomend the higher end components. Thats what happend when you ask a bunch of geeks

Part of their argument with recomending Corsair will be that they are very well built and very reliable. The smallest PSU they do is 450W.

Yeah, I'm looking at getting the corsair VX450W myself, and just suprised at how many people who have PCs that would run great on this PSU, will spend double the money by choosing a 600W+

that extra money could be much better spent on upgrading something else in the PC e.g. the price difference between the E6750 and E6850.

What I really don't like is where the poster asks "I'm on a tight budget and don't want to spend more than I need to on a PSU", and people are still reccomending (with bliss ignorance) the 600W PSUs! I just wish more people on here would understand the facts rather than just the ignorance of bigger is better.

Where the knowledgeable people have posted "never skimp on a PSU", what they mean is don't buy a £15 PSU like any of these http://www.ebuyer.com/UK/cat/Power-S...at/Extra-Value But I think it's being misinterpreted by too many people into meaning 'spend at least £70 on a PSU'.

[acrobat]

That sounds like it is a server system! So of course he'll need more power than 700W

Nope. Its just a nerdy lads anime porn and games system. He just has lots of money.

The reason I started it is because so many people post asking "what PSU will I need for this new system I'm building", and they always get told to get 500W+ (usually the corsair 520W or 620W). When it looks like the system their building would easially run on less than 400W quite hapilly. It seems people are advising them to waste money.

I'd say that is good advice, not bad advice. Maybe if they are making a celeron PC to use MS Word then its overkill.. But otherwise, I think its probably good advice. Those corsair HX power supplies are silent which is a big deal for a lot of people. But they are also very reliable, so highly recommended. And even if the person only has a crappy old graphics card now, they may want to upgrade in the future, and it wouldn't be very good advice to advise someone to buy a PSU and in 18 months they go out and buy a new graphics only to see their PC die, just because someone suggested a mickey mouse bargain PSU that didn't put out a stready voltage.

Now this is the first sensible post that has made some good points from looking at efficiancy charts of PSUs, they do peak at max efficiancy at mid usage BUT a system is never constantly under full load unless you're doing stress-test benchmarks on it. Your argument about a PC being on 24/7; How often in this 24/7 usage is it going to be run at full power? 99% of the time the power hungry components will be idle, so on our example system, the PSU will be running at half power (probaby even a lot less).

It doesn't matter so much how much its stressed though, it matters that its being used. My last PC for example, I did work on it in the day, and then in the evenings I played games and watched films on it. So not everyone has a PC that gets as much use as that, but many do. So its not being run into the ground exactly, but its still being used a lot, and I never switch my PC off when I go to bed. Its always doing something at night, whether thats downloading a large file or running virus checks or defragging all the disks etc. So you run a PC like that for a few years or more, and it will definitely lose a portion of its overall power. When you then consider that, like someone else said, a pair of GTX's and an overclocked quad core, is pushing 650W without even including all the hard drives and other stuff that runs off the lonely PSU... you could really risk your PC by skimping on the power. In that example, my Corsair HX 620W would die under those circumstances, and may even take out other components with it. Then factor in the 24/7 usage for many years, and it all adds up. Best thing someone can do, is direct people to a good online PSU calculator. Then they can see for themselves how much power they will need.

Again, these are the MAX ratings when the components are being stress-tested; under normal conditions a PC gets nowhere near that.

Thats not necessarily true. It depends what a person uses their PC for obviously. But still, as mentioned above, a pair of 8800GTXs and an oveclocked quad core can push the 650W mark, and when you play a really high end game, all those things can, and will, be pushing the CPU and GPU's to their max. So theres 650W right there. You then add in your keyboard and mouse, god knows how many hard disks, and any USB devices, etc.. and the power useage of an average gamers PC can be massive. Sure, it may only be occasional high peaks, but that doesn't matter. It doesn't matter how frequent those peaks are, what matters is that if theres not enough power to meet those peaks, then that person's PC is screwed. So you need enough power to cover all eventualities.

Theres also the sensible idea of just getting a bit more than you need too, to future proof yourself - if only slightly. So some will want to future proof themselves more than others. But if you buy a lot of high end gear now, and then plan to buy a better graphics card at some point, and maybe a load more hard disks, and in a year... what was once a £650 CPU might only be £150.... So doing a little upgrade in the future would likely mean you have to take our your PSU from your case and fit another one - unless you future proof yourself now. So buying an 800W or whatever now, might seem like a good idea in 12 months when you come to upgrade, and you don't have to worry about your PSU.


----edit----
Infact... I wish I future proofed... I spent a fortune on a Corsair HX 620W and even this isn't enough I have an E6600 and an 8800GTX, but I want to buy a better quad core (The Quad core equivalent of this CPU is now £50 cheaper than what I paid for this chip... ). Ive recently bought a bunch of backup hard disks, so if I added a quad core to this PC, I don't think I would have enough power So my 80odd quid or whatever I spent on this Corsair 620w PSU was a big waste of money. Because I will need a bigger one soon, so this one will either have to go in the bin... or I'll have to go through the hassle of selling it on ebay or whatever. Probably to people who are also looking at quad cores and thinking, "Hmm that 620W looks a bit small", so I'll probably get about 10p for it.

[Blitzen]

what they mean is don't buy a £15 PSU like any of these http://www.ebuyer.com/UK/cat/Power-S...at/Extra-Value

Why not....that would run a Quad core and 6 8800GTX's and still have loads of headroom

Truthfully though, just buy what your budget dictates.
We all buy loads and loads of things we dont need or that are overkill but thats part of the fun.

On another note, how many people have problems with their rigs with big powered PSUs as opposed to the 'Scraping By' PSUs that others have?

I know full well that if my pockets would allow it, i would be buying the best bits all the time. Maybe it would be better to have an 'Enthusiasts' section here and another section called 'Sensible' section. This way everyone would be happy.

[Clunk]

Again, these are the MAX ratings when the components are being stress-tested; under normal conditions a PC gets nowhere near that. So it makes sense when the PC will rarely be drawing it's max power, that the PSU will rarely be demanded for it's max power.

But why bother buying the top end bits in the first place if you arent going to have a PSU that will let them work at their limit.

A good gaming session will max out both cards and the CPU easily, and all the other stuff is on by default, so I have to disagree with your argument.

Can I ask what PSU you have?

[Andaho]

Thanks for all the time you've spent with that long reply acrobat But I still find it hard to imagine that your 620W psu is not enough for when you upgrade... I draw that conclusion because a lot of the reviews I've looked at have monitored the drawing of watts of top-of-the-range PCs from the socket while testing.

As for PSU calculators; everyone says that all the PSU calculators way over-estimate, and when I put my proposed system in a few of them, they all said around 380W (a E6750 with X1950XT and 3 SATA HDs and 2 DVD-RW - with all the usual other stuff as well), so with the PSU calculator over-estimating, I'm going to have a fair overkill myself with the VX450W. A 300W would probably run the system flawlessly, but I still want to still be able to use it in several years time, and be able to upgrade.

[nickp8]

I have a Zalman ZM-MFC2. This unit has a CVS unit. The power cable from your mains plugs into the CVS and the power cable from the CVS plugs into your PSU.

The Zalman shows the real time power usage of the pc. The pc in my sig + 5 led case fans uses under 110W in idle. System runs fine on an Enermax Liberty 400W PSU.

I know people running Shuttles with C2D tw0 hard drives, optical drive, a 8800 with the Shuttle 300W PSU fine.

[Phil_P]

Now this is the first sensible post that has made some good points from looking at efficiancy charts of PSUs, they do peak at max efficiancy at mid usage BUT a system is never constantly under full load unless you're doing stress-test benchmarks on it. Your argument about a PC being on 24/7; How often in this 24/7 usage is it going to be run at full power? 99% of the time the power hungry components will be idle, so on our example system, the PSU will be running at half power (probaby even a lot less).

Thank you!

All my PCs run 24/7 at full load - it's called Distributed Computing (DC), but I take your point

[Andaho]

Can I ask what PSU you have?

I currently have the cheapest crappest PSU possible - it came included with a £30 case.

It has Pro-V CTW-325W written on it. It's in my current PC which is an Athlon XP 2800 with 1gb ram, 3x HDs (80gb, 320gb & 500gb), 2x optical drives 1 PCI card (a DVR video capture card) and a 6600GS.

It's been running in this PC for 4-5 years and I've never had any problems with it. I also leave my PC on 24/7 for downloading stuff overnight.

I haven't built a PC in the last couple years, but the budget one I built for a friend a couple years ago was a cheap colors case, and came with a 400W PSU, and I recently had to replace it for him, and replaced it with a 400W hiper.

I've never heard of anyone that has actually had a PSU that blew and took components out with it, so it must be a pretty rare thing? - I hear lots of talk about people saying "don't buy cheap because it might happen", and seems like it's an exaggerated fear. I actually worked at a (rip-off) computer shop for 6 months last year, and saw about a dozen of PCs with dead PSUs come in, and at the shop they change the PSU for a £15 one (and charge £89 inc vat and fitting), and give it a 12-month warranty, and never got any back.

I'm going to buy a VX450W for my new build, but I feel that most of these expensive PSUs are over-rated.

[Andaho]

Thank you!

All my PCs run 24/7 at full load - it's called Distributed Computing (DC), but I take your point

LOL, but my argument is about general computing what the hell do you use that setup for?

[scorpio05678]

i have just build a top end PC, i ll be using it for my dev work and for gaming for next 4-5 years. I got 800 PSU coz of my quad core and 8800 GTX 768 OC.

while doing Dev (pure caclutations no graphics involved) i am expecting it to churn at 60-75%, ORCAS + SQL 2005 will squeeze lot of juice.

and i don't want to change in another 2 years so little bit buildin contengency.

SC

[ed^chigliak]

If like me you know you are never going to run more than a single graphics card and a single HDD drive (minimum noise and heat with adequate performance) then excessive headroom is a complete waste of dosh. If I was to think it's a one time only purchase so I'll buy me a 1kw PSU and it will last a lifetime well it won't cos all those darn connectors keep changing shape. A budget of £35-£45 will buy me a decent 400-500W PSU which in theory will run perfectly well up to the rated power. I have used FSP, Antec, Seasonic, Enermax, Thermaltake, Xclio and had zero problems with any of them.

If you know you're the type of person to add 10 HDDs buzzing away in your rig instead of doing something sensible (imo) like building a NAS server then fine. They got just the right PSUs for you too.

Just recommend a PSU appropriate to the individuals needs. Money is nearly always better directed into the graphics department for a gaming rig and everything else is simply needs to be adequate. No obvious bottle necks and a PSU that won't explode but at the same time isnt overkill.

[amjedm]

Andaho - I've just seen your "My System" spec on the side and must say it's one decent system you're running on that 200W Lian Li PSU