PSU Question

Dempsey · 15-09-2003 5:37pm #1

Would a P4 800MHz FSB and lets say a 9800Pro (with its power requirment) be able to run off a 300W PSU? I know a 300W PSU works a P4 but would it be able extra strains?

Dooom · 15-09-2003 5:45pm

id be doubtful, the minimum power requirement for the 9700 pro was 350w. but it does depend on how good the psu is...a good name 250w psu would be better than say a 400w no-name (crap name) psu...or something along those lines

BoB_BoT · 15-09-2003 7:21pm

ok this confuses me a bit, how can a "no name" psu that's 400w be less powerful than a "brand name" 250w? I've heard someone else say this before, but it just doesn't make sense to me. Can someone clarify it?
Thanks

jonhate · 15-09-2003 7:43pm

Usaully Better known power supplies will take a higer load on their voltage lines.

SickBoy · 15-09-2003 7:49pm

It's to do with the rails on the powersupply.
If your 12v rail is only able to supply your system with say 11v then the components being supplied by this rail will not be happy and will be unstable. The same goes for the 5v rail and 3.3v rail.
So no matter how many watts the PSU is rated, be it 250w or 500w, if it can't supply the correct voltages its poo...
This may be 100% wrong but that's my take on it.

BabyEater · 15-09-2003 8:05pm

When looking at power supplies check out the 3.3v+5v combined outputs.
e.g. if you have a 300 watt psu you want about 160watts on the 3.3v and 5v combined.

Red Alert · 15-09-2003 8:56pm

Basically, as you draw off more power (more milli-amps or amps) from the rails, the rail voltage will decrease.

In a good PSU, the rail voltages won't change very much as it approaches its maximum loading, whereas in a crappy PSU, these rail voltages will start dropping once you pop in a PCI winmodem!

RicardoSmith · 15-09-2003 9:11pm

Originally posted by Red Alert
Basically, as you draw off more power (more milli-amps or amps) from the rails, the rail voltage will decrease.

In a good PSU, the rail voltages won't change very much as it approaches its maximum loading, whereas in a crappy PSU, these rail voltages will start dropping once you pop in a PCI winmodem!

Yeah. You don't need a 600w PSU you just need a qood quality one. That siad I've never had any problems with PSU's ever. Even with cheapo underpowered ones.

Creamy Goodness · 15-09-2003 9:14pm

you need a 420w minium because i have a p4 800mhz and when i tried making a system with a qtec 400w psu it didn't work tried my mates cheiftec 420w and it worked then i bought one myself

BTW don't try to save money on a power supply your going nowhere fast without it mate

Dempsey · 15-09-2003 9:34pm

I have a case here with a Q-Tec 350W PSU. The mobo will be(as of tomorrow:) ) an Abit IC-7 G. No 9800Pro(I was using the worst case scenario for power), but will be getting a 9600Pro. No CCFL's or anything, just a plain and simple pc. would 350 not do it?

I have to get a 420W PSU.:mad:

I have to get a case fan too, could anyone recommend a right good one?

Creamy Goodness · 15-09-2003 9:39pm

dempsey i have the same board nice one it is

but it won't run on a 350w of any make EVEN Qtec they are the worst PSU going

get a cheiftec antec or enermax

they cost more but like i said before youre going nowhere without a quality psu

astrofool · 15-09-2003 9:40pm

i got a supermicro PWS-024, 400w rated.

Now Amps = watts x volts (source: http://www.astronomysite.com/mapug/19/msg20152.htm so this may be wrong)

but working it out using this page:

http://www.supermicro.com/PRODUCT/Accessories/Power_Supply.htm

gives 300w on the 12v rail, 225w on the 5v rail and 100w on the 3.3v rail

Is this right, or is my maths wrong ? because that far out-rates most 400/550w psu's out there

Creamy Goodness · 15-09-2003 9:42pm

i was trying to run the board on a qtec 400w psu

and it cut out during xp install and i was ripping my hair out to find out what was going wrong then i switched psu and it worked

happy overclocking (if thats what your doing)

Dempsey · 15-09-2003 9:45pm

Originally posted by Cr3m0
but it won't run on a 350w of any make EVEN Qtec they are the worst PSU going

get a cheiftec antec or enermax

Didnt know that they were a bad PSU, **** them anyways.

what about a codegen 300W, is this another lemon of a PSU?

BadCharlie · 16-09-2003 8:17am

Can a underpower PSU damage your computer in any way ? Thats what i be worried about.

Scruff · 16-09-2003 10:08am

i was going to buy the Q-Tec PSU ATX 400W Dual Fan as part of my upgrade to an antlon xp 2500+. Are these power supplies complete ****? Should i stear clear of these altogether?
Trying to keep costs down so what is a decent, relitivley cheap psu?

netman · 16-09-2003 11:20am

lads, stay away from cheap PSU's.. there's no point in spending loads of money on quality components and then not give them a good power supply.

with a lot of the "no-name" power supplies the only thing different between a 300w and 600w models is the sticker. open them up and you'll get a real shock of how crappy they are.

to answer the question can a bad PSU damage anything inside your computer - well, yes, in some cases. some PSU's when overloaded might burn out and the cheap ones in general don't have overload protection and won't power down, but fry your components instead.

another thing to consider is the fact that most cheap power supplies don't meet the advertised specifications. some of them fall 30% short off the rating on the sticker.

computer components don't react well to voltage drops, especially processors, so a stable voltage is a must for stable operation. if you can live with your computer crashing whenever it draws too much power from the cpu - fine. if you can't - get a PSU that can supply the correct voltage even under heavy load.

another very annoying thing for me are the fans. it seems everybody overlooks the noise psu's make. you'll find models out there with three fans, all of them screaming. last thing i want to have in my room is a computer that sounds like a hoover! look for "noise killer" PSU's - ones with thermally controlled fans, or manually adjustable.

Here's a good round up of current power supplies that goes a bit more in-depth:
http://www4.tomshardware.com/howto/20030609/

An older review covers 21 power supplies under heavy load:
http://www4.tomshardware.com/howto/20021021/index.html

A short article about cheap power supplies and risks:
http://www4.tomshardware.com/column/20011012/

If this all is too much for you to take in, just stick with good brands and you'll be safe. 350W should be enough for a modern PC, and have a bit of headroom for upgrades. enermax, antec, fortron, enlight, aopen, zalman and pc power&cooling generally make good PSU's.

Personally, I shelled out a bit more cash for something hopefully future proof that won't give me any headaches, and it's worth it simply for the peace of mind.

Virus_Inc · 16-09-2003 12:09pm

As the saying goes: Lies, damn lies and power ratings on cheap power supplies.

Cheap power supplies are like those nasty little midi systems (where noise masquerades as sound) that advertise themselves as 2000W PMPO!!!

A good rule of thumb is the rule of weight. If it's heavy then there are lots of fat heatsinks inside it which are expecting and can deal while lots of power.

Here is a good description I found on a review site...

The PSU is far from the most expensive component in most modern PCs - most no-brand clone PCs use the PSU that came with their case. Stock PSUs in half-decent mini-tower cases are likely to have about a 250 -300 watt rating

By itself, one of these yum cha PSUs will commonly have a retail price of less than $US15.

If you're now thinking that it doesn't seem too likely that a $US13 PSU will be the most carefully designed and manufactured electronic device in human history, you're on the right track.

If your PSU's no good, it can cause amazingly diverse problems. Underpowered or otherwise defective PSUs don't necessarily have the decency to just go pop and stop working, you see. They may do that - or they may decide to go out in company, and pass mains voltage through to the motherboard. But they're more likely to just suffer voltage sag.

Voltage sag is your own little private brownout inside your computer case.

The three primary output "rails" from a modern PSU - the only outputs that have to supply a lot of current - are the 12V, 5V and 3.3V lines. Overloading one of them can make all of them sag, depending on the PSU design; lousy PSUs may also deliver too high a voltage under some circumstances, or have a lot of "ripple" - a regularly varying output voltage.

Different computer components have different tolerances for low input voltage and other supply oddities, and will foul up in different ways when underpowered. Most of these ways are unlikely to give you any obvious indication that it's the PSU at fault. If you don't know the PC service-person's mantra - "if the problem's bizarre, try another PSU" - you can waste days swapping boards and changing drivers and fooling with your RAM configuration, and still have a computer that flakes out whenever, for instance, all of the drives are accessed at once.

So that's one reason to buy a more expensive, beefier PSU.

MoSeS_. · 16-09-2003 1:47pm

I'm at work now so I can't check the make of the PSU on my machine at home, it's whatever came with my Yeong Yang Server Cube. It's rated at 350W.
At the moment it is powering
An Asus A7VN8X Deluxe running an XP 2400 at about 2.2Ghz at the moment.
Radeon 9800 Pro 390/375
2X512MB @ approx 155Mhz
2X 120G Seagate Barracuda @7200 RPM
Hauppauge TV Tuner Card.
Toshiba DVD ROM
1 80mm Case fan and two more of them on the radiator for the watercooler all running through a Noise Isolator variable resistor bank with blue LEDs.
I added a water block to the Radeon and the Northbridge but up to the day before yesterday it was powering the fan on the Radeon too. (The waterpump is running directly off the mains)

So all in all a decent 350W PSU can run a machine with a 9800 pro
Although I don't have a noisey monster fan cooling the cpu, they could be a bit of a drain I'd imagine, hardly much more than an additional 7200 RPM drive which I have had hooked up on occasion.

But it's no harm going for 400+ if you've a bunch of fans and a few hard drives.

Creamy Goodness · 16-09-2003 5:19pm

in my experience i'd avise people to Stay away from Q-tec of other cheap power supplies

as netman said

lads, stay away from cheap PSU's.. there's no point in spending loads of money on quality components and then not give them a good power supply.

couldn't put it better myself

Dempsey · 16-09-2003 5:26pm

Originally posted by Cr3m0
in my experience i'd avise people to Stay away from Q-tec of other cheap power supplies

as netman said

lads, stay away from cheap PSU's.. there's no point in spending loads of money on quality components and then not give them a good power supply.

couldn't put it better myself

Should i try and sent back my case? I got it monday, If i knew then what i know now, id never have bought the case off them. Or jsut go hunt for a good PSU, any recommend a good place for buying PSU's?

Creamy Goodness · 16-09-2003 5:32pm

dempsey are you happy with your case?

if you are then hunt down a quality PSU

i recommend this one

it's the one i have and i'm running

Abit IC7-G
P4 3.0ghz
1GB RAM
128mb geforce 4
30gig sata 10k rpm drive + 120gig 7200rpm
audigy 2
and several case fans
along with usual floppy and cd drives

Dempsey · 16-09-2003 5:51pm

Hmmm, nice but its expensive considering that i've forked out money for a case with underpowered PSU, only having to get a another PSU. Yes, I do like the look of the case but im really annoyed about the PSU after hearing what you have said.

RicardoSmith · 16-09-2003 9:49pm

LIke I said earlier I've never had a problem with a PSU ever. In Offices with hundreds even thousands of PC I've only ever seen one PSU spark up and a handful of them die. Never seen one cause damage to another component.

Has anyone in this thread ever personally had a problem with one? I've a couple of cheapo ones that have been going for years, and they've been hacked in and out of various machines. My little terminator PC has a 150W PSU and that has been as solid as a rock. I've filled it with drives of all kindsa too. Look at the shuttle systems they all have low powered PSU's and can run P4 3ghz and mutliple drives no problem. Most of the OEM's like Dell all have low powered PSU's too. My advice is don't worry about until you have a problem. You most likely won't.

Creamy Goodness · 16-09-2003 9:53pm

this is the case i got and it didn't come with a psu

plus i had to go out and buy that psu on top of it

that case cost £111 sterling

BeatFreak · 16-09-2003 11:16pm

As confirmed allready by earlier posts a good quality "good name" psu is very important I think my system is a good example of this, all the following are running on an enermax 350W psu.

2600 AMD Athlon XP @ 2550 megahertz
512mb Corsair Twinx PC4000 Dual DDR kit
Abit NF7-S V2.0
MSI MS-StarForce GeForce4 Ti 4800
Sound Blaster Audigy 2
WD Caviar 120 gig 7,200 rpm HD
ASUS CRW-4816A.
Samsung 16/48 DVD
CPU cooling: Vapochill PE (Titanium)

I know for a fact that the vapo sucks a huge amount of power and requires a high powered psu but this enermax is holding up just fine at the moment.
Im also in the process of deciding what GFX card to upgrade to but it's gonna be high powered (Radeon 9800XT most probably) I'll try it on the 350 but I more than likely will have to upgrade to the enermax 550watt.
On paper 350 does'nt sound like alot but, the above proves a good psu will hold any system better than any 600 watt "no-namer"
Hope this helps.
Dev.

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