Power Supply Units

nah ya just wrong

[Lister of Smeg]

Originally Posted by ooogemaflop

nah ya just wrong

If you'll look at the sticker on the side of any power supply, you'll see the ratings for the various voltages supplied. Modern PCs draw most of their power off of the +12V rails, so it's the total available current/power available on the +12V line that determines whether or not your power supply has enough capacity.

Take a look at the sticker on the side of a high quality PSU rated at 560 watts fro example.

46 amperes (552 watts) on the +12V rail is more than enough for any PC with a single graphics card, and it's good enough for mid-range two-card Crossfire/SLI set-ups, as well.

Anything over 30 amperes should be plenty for most single-card PCs.

A cheap junk power supply claims to be a "550-watt" unit (almost exactly the same as the 560-watt Performance PSU). It's really only a 400-watt unit, rated at 25 amperes (300 watts) on the +12V rail

[Stuart]

Originally Posted by Lister of Smeg

So you're saying if he has an sli setup quad core 4+ GB of RAM and is using a cheap & nasty 500W winpower, he is not likely to fry his machine!

---------- Post added at 22:03 ---------- Previous post was at 21:59 ----------



I would only ever recommend a value PSU for just that basic use i.e. for a office machine or just browsing the web.

A Cheap PSU...

Is very unlikely to supply the stated wattage - none of the cheaper ones do

Not a problem. If she is looking at a 400w PSU to replace a 250W one, it's unlikely to drop below the 250 (even assuming the PC uses anywhere near 250W).

Is very likely to be noisy, either immediately or after using it for a short while

Likely being the operative word.

It might not have enough connectors or the right sort

Might not. If she has multiple HDDs, Graphics cards or Optical drives. This isn't likely if she is replacing a 250W PSU, because she would have needed a larger PSU before now.

It's very unlikely to be '80 plus' certified http://en.wikipedia.org/wiki/80_PLUS

It's a false economy basically, but if you must use a cheap PSU get one at least 100W higher

False economy, although it's one she may have to put up with if she can't afford the extra for an 80+ certified PSU.

there are thousands and thousands and thousands of systems sold a year by various big companies in the under 500 quid price range and I would venture a huge % of these have very cheap and basic PSU's and of these systems the vast majority will last the year warranty and well into 3 4 or more years after. Some will fail but so will some of the expensive ones. A basic PSU should be perfectly adequate.

Even if it fails who can say the £60 quid model wouldnt have as well

[Lister of Smeg]

Originally Posted by ooogemaflop

there are thousands and thousands and thousands of systems sold a year by various big companies in the under 500 quid price range and I would venture a huge % of these have very cheap and basic PSU's and of these systems the vast majority will last the year warranty and well into 3 4 or more years after. Some will fail but so will some of the expensive ones. A basic PSU should be perfectly adequate.

Even if it fails who can say the £60 quid model wouldn't have as well

Talk about moving away from my question.

You will also note a value PSU will only come with a 12 months warranty whereas most Performance PSU's come with between 2 to 5 years. IN the long run, a conformance PSU is the way to go whether it's for the warranty or that you can put your mind at ease that it's not guna fry and take everything else with it.

[progers]

Have you thought of e bay?

I've used arthur1113 in the past, he sells used but tested PSUs at around £10

Originally Posted by Lister of Smeg

Talk about moving away from my question.

You will also note a value PSU will only come with a 12 months warranty whereas most Performance PSU's come with between 2 to 5 years. IN the long run, a conformance PSU is the way to go whether it's for the warranty or that you can put your mind at ease that it's not guna fry and take everything else with it.

I aint gonna agree with you in this instance, a different machine might lead to a different response but no stock answers here mate each solution I offer is catered to the individuals requirements and I am very proficient ( and arrogant) about the quality of said support

[Stuart]

Originally Posted by ooogemaflop

there are thousands and thousands and thousands of systems sold a year by various big companies in the under 500 quid price range and I would venture a huge % of these have very cheap and basic PSU's and of these systems the vast majority will last the year warranty and well into 3 4 or more years after. Some will fail but so will some of the expensive ones. A basic PSU should be perfectly adequate.

Actually, on this occassion, I agree.

At work, we have hundreds of PCs. I don't have knowledge of every part of every one, but I dare say that they (with very few exceptions) would have the cheapest PSU our supplier could get away with. We have a failure rate of between 1 and 5%. A fraction of those are power supply failures (in fact, more often that not, it's a memory or HDD failure).

[Graham M]

Originally Posted by Stuart

At work, we have hundreds of PCs. I don't have knowledge of every part of every one, but I dare say that they (with very few exceptions) would have the cheapest PSU our supplier could get away with. We have a failure rate of between 1 and 5%. A fraction of those are power supply failures (in fact, more often that not, it's a memory or HDD failure).

And the majority of these are on 24/7 I would guess?

[Gavin78]

Thought I would pop in and say I am running a 850watt psu £25 from my local market stall selling computer parts. I've never had a problem with them over the years.

Its powering a dualcore cpu 7850 BE, geforce 260gtx, 8 gig of ram, 4 HDD's (5 when external is on) 1 DVD drive (2 when external is on) laser printer when on and a creative sound card.

So far so good for 2 years now no problems with it (apart from the 3 pin socket is a little loose)

Just bought another from Ebuyer though a better branded one for my new build 900watt.

Thought I might add that when I first got into building pc's 1999 I didn't have a clue, first time round I screwed the mainboard onto the back plate without the brass pins in place to mount it and totally fried everything (myself included if I would have touched the case when I turned it on) its a shame really I took the tower unit to the guy in the shop and he just looked at me like an idiot when he saw what I had done. I was lucky he gave me a new board (cpu was fine)

2nd time I did it right only months later I tried to plug a cd writer in while the pc was switched on and the power cable sparked at the back of the cd rom and the pc shut down, it wouldn't start for about 10 minutes, after that it never worked right and it killed the graphics card as it never work 100% after that.

Lesson learnt over the years.

[Stuart]

Originally Posted by Graham M

And the majority of these are on 24/7 I would guess?

Actually, no. Most are normally shut down around midnight and restarted via WOL between 8 and 8:30. Or so I understand (I am never at work at those times, so cannot verify that).

[Graham M]

OK fair enough, still a relatively long day to be spent on so-called "Cheap & Nasty PSUs"

[Stuart]

Originally Posted by Graham M

OK fair enough, still a relatively long day to be spent on so-called "Cheap & Nasty PSUs"

It is, and sort of backs up my point. We make heavy use of PCs, still have a relatively low failure rate.

It's worth noting, however, that the bulk of these machines are lab machines, and while we do allow students to store stuff on them, we expect them to back up anything they need to keep, and do not store anything we need on those machines. As such, it does not affect us if the information on the machine is lost.

Staff machines are a different matter, and these do often come with good quality power supplies.

As for the the servers, these also come with good quality PSUs (generally including redundant PSUs as well) and are backed up regularly.

[damien c]

Originally Posted by Lister of Smeg

So you're saying if he has an sli setup quad core 4+ GB of RAM and is using a cheap & nasty 500W winpower, he is not likely to fry his machine!

---------- Post added at 22:03 ---------- Previous post was at 21:59 ----------



I would only ever recommend a value PSU for just that basic use i.e. for a office machine or just browsing the web.

A Cheap PSU...

Is very unlikely to supply the stated wattage - none of the cheaper ones do
Is very likely to be noisy, either immediately or after using it for a short while
It might not have enough connectors or the right sort
It's very unlikely to be '80 plus' certified http://en.wikipedia.org/wiki/80_PLUS

It's a false economy basically, but if you must use a cheap PSU get one at least 100W higher

I have ran a system with a high end dual core AMD cpu overclocked with 2 8800gts's in sli with, 3 hdd's and dvd etc using a cheap and nasty 700w power supply.

I had to use the molex to pci-e adaptor's to get enough and they worked fine.

I ran that system for about 6 month's until I upgraded the whole system including my power supply.

That cheap and nasty power supply is still going strong today after being used everyday for over 2 years, and will probably carry on till I have to change it or just throw it in the bin.

Just because they are cheap does not mean they are poor power supplies, sometimes they can surprise you and be better than the high priced ones.

As for the 80+ thing that really is only required for multi card setup's as a single card does not require a 80+ power supply, most will only require a normal power supply and most now are 80+ anyway.

[Lister of Smeg]

Originally Posted by damien c

I have ran a system with a high end dual core AMD cpu overclocked with 2 8800gts's in sli with, 3 hdd's and dvd etc using a cheap and nasty 700w power supply.

I had to use the molex to pci-e adaptor's to get enough and they worked fine.

I ran that system for about 6 month's until I upgraded the whole system including my power supply.

That cheap and nasty power supply is still going strong today after being used everyday for over 2 years, and will probably carry on till I have to change it or just throw it in the bin.

Just because they are cheap does not mean they are poor power supplies, sometimes they can surprise you and be better than the high priced ones.

As for the 80+ thing that really is only required for multi card setup's as a single card does not require a 80+ power supply, most will only require a normal power supply and most now are 80+ anyway.

Generic PSU's often don't fail safe. That is, when that day arrives (probably sooner than later) when the generic PSU fails/stops working, it will take out the hardware components with it. So again, this is just another reason to purchase a good quality PSU.