Possible Problems for Puny PSU

Fanny Cradock

Alliteration aside, as you may or may not know, I was on a couple of weeks back about a new build. The packages are due to arrive this week - weather permitting, of course. However, I've just had a moment when I realised that my penny-pinching might be coming back to bite me.

Initially I calculated the power requirements of the build with a HD 5570. I figured that I could easily drop to a 450w PSU to save a bit of cash and still have watts to spare. Later I changed the card to a GTX 460 1gb, which is considerably more power hungry, but neglected to factor this extra consumption into the final version of the build. Now I'm seriously beginning to think that the PSU wont be able to handle the load put on it - at least in the long term.

Using the above calculator, I'm getting a figure over 483w - that's with a high value of 30% capacitor ageing and assuming a PCI IDE is the same as a wireless card. This drops to 412w at 10% ageing. I'm assuming that without any ageing included the PSU should be able to handle the power demands placed upon it at least initially. Which I hope means that there isn't an immediate problem.

Anyway, below are the values I entered. In the long term (say a year or so) I guess I'll be needing a new PSU. But I'm more concerned with the immediate power shortage problem, if indeed there is one.

Advice?

deconduo

If its the super flower amazon, you should be fine.

Fanny Cradock

Yeah, it's the super flower 450w.

I'm a little wary of using these type of calculators. How often would the cpu and system be under 90% load? And does the optical drive, which takes about 30w, draw power when it's not in use? I suppose if worst came to worst I could always disconnect the optical drive because I never use it.

Do you think I would need to replace the PSU at any stage?

Solitaire

So long as its no higher than a 95W TDP CPU and you don't OC anything or add one-billionty 3.5" HDDs you'll be fine. ~7A for a tri-core AM3 or an i5 quad, ~12A for the card, ~3A for system/mobo/drives/fans, and you get a worst-case average draw of 22A - only two-thirds the 33A rating of the Amazon 450W. Not fantastic (I prefer it to be closer to 50% load) but perfectly acceptable and not unnecessarily inefficient either

BTW those calculators are a pile of **** :P

Fanny Cradock

Solitaire wrote: »

So long as its no higher than a 95W TDP CPU and you don't OC anything or add one-billionty 3.5" HDDs you'll be fine. ~7A for a tri-core AM3 or an i5 quad, ~12A for the card, ~3A for system/mobo/drives/fans, and you get a worst-case average draw of 22A - only two-thirds the 33A rating of the Amazon 450W. Not fantastic (I prefer it to be closer to 50% load) but perfectly acceptable and not unnecessarily inefficient either

I won't be indulging in any SLI business or adding any extra HDD's. And I can't imagine I'll start OCing after a lifetime of not bothering. Right now I'm more than content with the system I will have (I'm currently using a 3700+ 1GB 7600GT rig). And if there are going to be no power issues with the base set-up, which is what you both are suggesting, then my mind is put at ease.

Cheers, folks!

Solitaire wrote: »

BTW those calculators are a pile of **** :P

Yeah, I suspected as much!

Fanny Cradock

BTW, what exactly is TDP?

Solitaire

TDP = Thermal Design Power/Property. Basically, the maximum amount of heat a component can generate, and as silicon chips are naught more than giant arrays of electrically-operated switches, 99.999% of the electricity used in the process is given off as said heat, so for certain computer components TDP can be taken as a measure of power consumption as well as heat

Generally speaking most CPUs and graphics cards use nowhere near as much energy on average than their listed TDP. Most Core 2 Duos used 30-40W of power, yet were rated for 65W. Similarly, 45nm Core 2 Quad CPUs usually consumed 55-70W of power rather than the 95W TDP given. The power consumption of graphics cards can spike very high momentarily, so their average power consumption is often nowhere near the given TDP.

Fanny Cradock

The things you find out! Thanks.