How do you anticipate wattage when building a system?

[zaphox]

When you're spec-ing up a new system, how do you anticipate the wattage required from your PSU?

I can see on Scan that the CPU I'm looking at will take 125W and I can imagine a modern GPU will need at least that.. but what about the rest? Most items don't have that information (that I can see)

MoBo
RAM
HDD
CD/DVD ROM drives

I guess these items don't require much power, but how do you know how much when it's not listed on the retailer's webpage? Is there a general guide for these standard items?

[Sputnik]

Use this ? http://www.corsair.com/psufinder/ or http://support.asus.com/PowerSupplyC...tor_right.aspx

They will give you an Idea although not 100% accurate.

[Pob255]

well it can vary a lot depending on graphics card and such.
Basic rules of thumb
the two big power requirements are CPU and graphics card.
it's roughly 5-6 harddrives to the graphics card (approx 100w)

generally speaking for a single cpu and gpu with one or 2 hd's no more than 450w

[jim]

I've always used this site for a rough estimate, tends to be reasonable and pretty easy to use.

[aidanjt]

I've always used this site for a rough estimate, tends to be reasonable and pretty easy to use.

Yes, use that, then divide by 2 for actual power usage. :S

[jim]

As I said, rough guide. I'd always rather get more than less.

[aidanjt]

Well, there's 'rough guide', and there's way way way off.

[dave87]

It depends on what I'm building the system for.

If it is a lower power server, I'm never realistically going to need 600w or more, not if I want it to remain quiet anyhow. So for that configuration I'd opt for a decent quality PSU of the 400w mark.

However for my main system, I'd look at something a bit better. Now I know, for me personally, there is no point in a 1kw PSU that sounds like a tornado as I'll never use it. I opted for a decent Seasonic PSU, S12 500w as I am not going the SLi route. If I were, I'd be looking more at the 750+w range.

The crucial thing I suppose is efficiency and noise level - I chose an efficient, quiet PSU that fitted the components I was using without breaking the bank. If you want modular there are options for that too.

If it is a basic system have a look at the Corsair VX or HX range up to the 520w mark, if it is a gaming system or you want room for expansion, I'd look at the HX620 and above.

Hope that helps in general terms, if you give us an idea of the components we can perhaps provide some suggestions?

[TooNice]

Usually, I determine what graphics card I want to get, check out reviews from popular review sites. Most of them will have a page that measure system power consumption under load. Most of them also tend to use a system more powerful than I can afford (e.g. Quad-core in the 'Extreme range').

There will probably be some variations between reviews, but I'll go for the worse scenario. One or two sites also (try) to work out the actual power load of those graphics card. I'll add that to the total just in case I decide to add another card later on. Then I add another 100-200W in case I decide lots of HD and/or for future upgrades. By the time I will need more than that for upgrades, it'll probably be time for a new build anyway, especially if I stick with single GPU.

That adds up to about the 600-ishW for me. I went for the HX620 (but only because I got a decent deal and bought about a year ahead of my built - now I would probably go for a modular PSU of equivalent power).

[EarlGrey]

The lack of knowledge about powers supply requirements is a real shame. My ignorance included.

I had a power supply blow on me about a year ago, and just for kicks decided to put an old 300W supply in. This was a Q6600 and 7800GTX based machine. There was no PCI express power available, and every time I booted the graphics card complained about a lack of power (little dialog box) - but worked fine!

Having said that, good quality supplies make a huge difference to the stability and thus overclockability of a machine. I would choose a good brand, and make sure it has enough PCIexpress cables for you. That should guarantee it is capable of putting out the power you need.

[Sputnik]

The lack of knowledge about powers supply requirements is a real shame. My ignorance included.

I don't think it is soo much a lack of knowledge. Most of the problems with PSU's is that they are misleadingly rated. You would be lucky if half of the cheap supplies rated at 550watts could actually supply 400watts and then of course there is the lack of power consumption figures for other hardware.

[zaphox]

The crucial thing I suppose is efficiency and noise level - I chose an efficient, quiet PSU that fitted the components I was using without breaking the bank. If you want modular there are options for that too.

If it is a basic system have a look at the Corsair VX or HX range up to the 520w mark, if it is a gaming system or you want room for expansion, I'd look at the HX620 and above.

Hope that helps in general terms, if you give us an idea of the components we can perhaps provide some suggestions?

Sorry... what does modular mean in terms of PSUs?

The PC is for my boss, it will be a standard desktop mobo with an AMD dual core CPU using onboard graphics so I know it won't need much power. I'm looking at a Corsair 400W unit.. I just wanted to be sure that would be sufficient since he has quite a few drives, but from what I've read that will be ample.

[dave87]

Modular is the way of describing a PSU with which you attach only the leads you need.




If you look on the back of that PSU, there are various holes?

That means you can connect just the leads required = less clutter and less airflow restriction. It also means it is a lot easier to wire up the PC, as you have only to deal with the wires that you need

The Corsair model which is modular, is this one versus this non modular one

[zaphox]

Gotcha =) Cheers

[jim]

I prefer them as I rarely need that many extra leads, so it reduces a lot of the cable mess inside the case.

[scaryjim]

Assuming you're being sensible and using a 65watt CPU, an ordinary office PC is unlikely to draw more than ~ 100W at full load - and you're very unlikely to fully load a PC with normal office tasks. This Hexus review of an AMD motherboard might be of interest - the review uses a 45W CPU suggesting that around 50 - 60 watts is probably a good estimate of how much your supersystem (i.e. mobo + ram + peripherals) will draw. From there I guess your only real concern is how much overhead to allow in your system...

EDIT: I just found this article about HDD power draw. It's rather long-winded and worthy (as well as a few years out of date, I'm afraid), but uses *actual, measured current draw* on both 12V and 5V rails for a wide range of drives. It basically seems to show that most HDDs will pull low-teens during use, but 20W+ at peak / start-up.