PSU Advice

[Switch]

Okay, so I think I've narrowed down my recent crashing issue (see thread further down the forum) to my PSU. Probably. Either way I'm going to invest in a new one, as even if it isn't that that's causing it, I don't think mine is very good. It doesn't even seem to have 18A on the +12v rail.

 

So, I've had a look around, and these two have stood out for me thus far:

 

Corsair Memory 620W, ATX, EPS12V, PS/2

Tagan 800W PSU - Dual Engine (a tad more than I want to spend)

 

The first one appeals to me the most... it has an adequate wattage, and seems to have quite a few features, and a positive review as well. It also has a five year warranty, and a pretty good price for the quality of it. The second one, as I say, is a bit pricey, but it certainly has a lot of juice... though only three years warranty.

 

Opinions? Of course if anyone knows anything better for around the £50-100 range, please do suggest it... I don't know much about PSUs after all.

 

Oh, and not forgetting, my specs:

 

nForce3 250 Motherboard

AMD 64 3000+

1.5GB DDR SDRAM (200mhz all single channel)

NVIDIA GeForce 7800GS (AGP 8x), OCed by XFX and fitted with a custom XFX fan as well.

Maxtor 80GB IDE HDD (2 partitions)

 

According to an online wattage calculator, I only need about 300w for my setup... but may as well give myself a nice large margin.

[Marxist ßastard]

Mind this from the Corsair website, though:

 

http://www.corsairmemory.com/corsair/images/WEB_PS_3-TABLE.gif

 

It seems to me that the main difference between the CMPSU-620HX and the somewhat less expensive CMPSU-520HX is some extra current on the +5V rail, and a better ability to cope with a lot of power being drawn from all three +12V rails simultaneously.

 

Why are you looking at power supplies with three +12V rails, anyways?

[Dark0ne]

I don't think I've ever spent over £60 on a PSU, Switch, and mine have worked great (and my system has a higher spec than yours). I can't remember what mine is, since Overclockers have changed their really cool site format into an eBuyer/Dabs look-a-like, but I know it wasn't more than £60. Might want to save some coppers!

[Switch]

The reason I'm looking at ones with 3 12v rails is... because... I wasn't even aware it had 3 of them. Or even what that means, really. :P Like I said, I don't know much about these things.

 

Thanks for showing the 520W one though, that seems much more reasonable (as you say Dark0ne, the other one is rather overkill for my system). Even the 520W is probably overkill for my setup but hey, it sounds pretty good and is only £70... it may even last into my next build. So methinks I'll go with that, unless you think I'll run into any problems with it? Would I need to set it up in any particular way because of the 3 +12v rails? Also, it says it comes with 8 SATA cables... do those work with any component? And I have an AGP 8x card that requires a power connector, will it work with that?

 

I suppose my motherboard would also need to support SATA for it to work? If so, how would I find out if it does? PC Wizard and CPU-Z just say that my mainboard manufacturer and serial are "Unspecified", which is hardly useful.

[Dark0ne]

I'm still on IDE so I can't help you with SATA connectors -- I was unaware they had different power ports. If SATA does have different power ports then yes, you'll need SATA hard drives and it probably won't work with your AGP.

[Marxist ßastard]

I'm still on IDE so I can't help you with SATA connectors -- I was unaware they had different power ports.

IDE hard drives use the molex power connector. The newer SATA hard drives use their own power connector, which is shorter and wider, and gives them the +12V and +5V rails that IDE devices get from a molex connector, plus some +3.3V power, which they're free to use in low-voltage circuit designs.

 

Also, it says it comes with 8 SATA cables... do those work with any component? And I have an AGP 8x card that requires a power connector, will it work with that?

 

I suppose my motherboard would also need to support SATA for it to work?

If the power supply has extra connectors for PEG power and SATA, you don't need to use them. It is, however, important to make sure there are enough molex plugs to go around (since PEG power is supposed to replace molex/berg connectors on high-end video cards, and SATA power is supposed to replace molex connectors on hard disks). If you have to run molex splitters, then no matter how good your power supply is, you start to run the risk of overloading the wires leading from it to your devices.

 

So no, you don't need SATA hard disks to use a power supply with SATA power connectors, nor will there be any problem if you use an AGP card with a molex power connector in lieu of a PCI-E card with a PEG power connector --- you just need to be aware that it will be significantly easier on these power supplies to run out of molex plugs. Of course, if the power supply is modular, you can just throw away the SATA and PEG connectors, and hook in as many molex plugs as you want.

 

The reason I'm looking at ones with 3 12v rails is... because... I wasn't even aware it had 3 of them. Or even what that means, really. :P Like I said, I don't know much about these things.

 

Would I need to set it up in any particular way because of the 3 +12v rails?

Three +12V rails means the power supply can isolate the power used in the processor, a video card with a PEG power link, and another video card with a PEG power link --- EG, SLi. That's all well and good, but depending on some specifics, all your molex connectors may be grouped up on one single rail with the CPU, and they'll only be able to share the remainder of the 18A on that rail with the CPU. The remaining 22--32A would be reserved for PEG power connectors, which you wouldn't be using.

 

...But again, that depends heavily on the specifics of the power supply you choose. You may want to ask someone much more familiar with it how the rails are divided.

 

One final note: if the power supply doesn't come with a 24 pin-to-20 pin adaptor, you'll want to invest in one. They're very cheap, and could save you some major headaches if the power supply you do choose isn't compatible with your mainboard out of the box.

[Switch]

Wow that was a... lot of info, heheh. I'm afraid I'll need you to dumb that down some more, if you can.

 

First, some questions:

 

1: What's a molex connector?

2: What's a molex splitter?

3: How would the power supply be modular? I know with the HX520W you can connect/disconnect as many plugs as there are slots for them, but I don't know if the slots fit anything other than SATA connectors, it doesn't say... I would guess they're SATA only as they only mention SATA connectors being included.

4: What's a 24 pin-to-20 pin adaptor, and what purpose would it serve?

 

Three +12V rails means the power supply can isolate the power used in the processor, a video card with a PEG power link, and another video card with a PEG power link --- EG, SLi. That's all well and good, but depending on some specifics, all your molex connectors may be grouped up on one single rail with the CPU, and they'll only be able to share the remainder of the 18A on that rail with the CPU. The remaining 22--32A would be reserved for PEG power connectors, which you wouldn't be using.

 

...But again, that depends heavily on the specifics of the power supply you choose. You may want to ask someone much more familiar with it how the rails are divided.

Whoa er... what? Sounds rather complex. I think perhaps I best look for another power supply with just the one +12v rail... who would I talk to that's more familiar with it? Maybe if I just emailed Corsair...

[Dark0ne]

Let me try and answer the first two since I think I know..

 

The molex connector is the power connector that goes into an IDE Hard-drive (probably the one you're used too). It has 4 pins.

 

A molex splitter, I think, is something that you plug into a molex cable which splits into two molex ports...so if you've run out of molex connections you use splitters to gain more.

 

Hope that makes sense...finding it hard to describe!

[Marxist ßastard]

1. Darkminister Fullerene is spot-on about this.
   
2. ...And this as well. Molex splitters are like cheap power strips. They give you more outlets, but that doesn't mean they can necessarily handle everything you can plug into them. If you try to connect a power strip to one wall socket, then run more power strips off of that until you can plug in and then run a few dozen devices at once, you'll fail miserably --- the same thing happens if you try to run too many things off of one set of wires coming from the power supply (IE, one of the continuous "strings" of molex and berg connectors).
   
3. Modular power supplies give you a few connectors that provide lots of different rails at once instead of just having a gigantic tangle of wires erupting from the back of the unit. The idea there is that if you want a string of two molex connectors and one berg connector, instead of having to search through the bundle of wires coming out of your power supply for what you need (and basically being screwed if you can't find anything), you can instead just reach into the power supply's box, grab a length of wire that has the connectors you need, and then plug that into the power supply, at which point you'll be set.
   
4. Recently, mainboard manufacturers began following a standard that changed the 20-pin outlet that brings power from the power supply to the mainboard into a larger 24-pin outlet. Power supply manufacturers followed suit, and started building 24-pin plugs into their power supplies. If your power supply doesn't come with a 24 pin-to-20 pin adaptor and it has a 24-pin mainboard connector, the plug that's supposed to go into your mainboard just plain won't fit.
   

Corsair would probably tell you to contact Seasonic, since that's who actually designed and manufactured the component. You probably shouldn't bother, though, based on what this reviewer said:

 

Looking at the main PCB, we only see two points where 12V leads are soldered down. One labeled 12V1 and another labeled 12V2. For fun, I put a 30A load on the 8-pin EPS+12V connector. This should have tripped the PSU. It did not, which tells me that there is no OCP limiter set for this rail. I did the same with the ATX main connector and again the PSU did not trip.

 

http://www.jonnyguru.com/PSU/HX520W/IMG_0831.JPG

Above is a close up shot of the PCB and where the 12V wires all solder down.

This demonstrates that if the two rails are in fact separate, there is no OCP (over current protection) on each rail. Outside of a few traces zig zagging across PCB, I couldn't find how even 12V1 and 12V2 are separate, but I'm going to give Seasonic (the OEM for the Corsair units) the benefit of the doubt and say that we seem to have two 12V rails here, neither with any kind of "limit" on them.

It would appear that the three-railed power supply is... Not so much. All the better for you, though, since it essentially nullifies any concerns about rail separation. All in all, it looks to be a pretty solid unit.

[agent0002]

I don't think I've ever spent over £60 on a PSU, Switch, and mine have worked great (and my system has a higher spec than yours). I can't remember what mine is, since Overclockers have changed their really cool site format into an eBuyer/Dabs look-a-like, but I know it wasn't more than £60. Might want to save some coppers!

 

 

my PSU came with my 45$ case, and it runs really well.

 

more importantly:

 

there are only 2 ways i can chime in on this, im not sure if they will help that much

 

your first PSU, the corsair,has 1 120mm fan, and 84% effeciency. (and all ratings on newegg are 5/5)

 

your second one lists "dual push-pull fans", and "over 80%" efficiency. it also has no reviews at all on newegg.

 

being that the second is more expensive, and only someone running LOTS of stuff can use even half the rails on it, if i was you i would just get the corsair one. the second one probably has 2 80mm fans, which could be loud (if they were 2 120's that would be overkill), and the over 80% efficiency is alittle vague. also, corsair is a huge brand (albeit not for making power supplies, but big all the same). i have never bought a PSU, or needed to look for one, but i have never even heard of tagan. and i have bought quite a few computer parts.