Purchased 4650 with 400W PSU...

[Eluros]

Greetings,

I received an out-of-use PC as a gift, and am planning on turning it into an HTPC while spending as little cash as possible. Here are the relevant specs:

MoBo: Asus P5N-E
RAM: 1 GB DDR2 (one stick; I hope to add another, later)
CPU: e8400
2x IDE DVD Reader/Writer
3x Case Fans
1x SATA HD (7200 RPM)
1x USB Wireless Adapter (draws power from PC)

PSU: 400W, crappy generic brand. Only Molex connectors.

I want to convert it to an HTPC, and picked up a Radeon 4650 for $20 on Newegg during a sale yesterday. However, I'm concerned with whether I'll need to purchase a new PSU. The card comes with an adapter to convert the Molex connectors to the 6-pronged (I don't know the name of the connector off the top of my head). I've plugged my hardware into a few online calculators, and they say it should be okay; however, given that I don't know the efficiency of the PSU (but I'm sure it's terrible), and it's only 400W (the minimum for the GPU), I'm concerned.

My wife doesn't want me to spend any more money than necessary, and given that I already bought a new GPU, shelling out cash for a new PSU would not be ideal. However, if that's what I need to do, I'll do it.

Any tools you'd recommend I use to determine if I need a new PSU? Anyone have direct advice about my quandary? Should I try it and see-- at the risk of frying hardware? I'm normally all about being safe and having wattage to spare, but this is an unusual scenario (receiving a free PC and trying to maximize its use).

Thanks!

 

[ModestGamer]

There are a number of non modular PSU's in the $50 range around 600w that will suit your needs.

 

[fffblackmage]

Your current PSU will work.

If that doesn't work, you could get something like an Antec Earthwatts Green 380W or Corsair CX430. I think the Earthwatts Green is the better PSU, but the Corsair is cheaper after a rebate.

 

[veri745]

Which "crappy generic brand" is it? It might work, but any of the no-name brand PSU's are a gamble. Some can't even output 50% of their rated load, just check the PSU article that Anandtech recently ran: http://www.anandtech.com/show/3985/three-550w-psus-for-different-prices

I wouldn't risk using a crappy PSU, but it might suit your needs just fine. I haven't had a generic PSU take other components out with it, but I've definitely had a couple fail on me. A dead mobo is just a few amps away.

 

[Eluros]

Thanks, everyone, for the suggestions, comments, and links.

Which "crappy generic brand" is it? It might work, but any of the no-name brand PSU's are a gamble.

I'm at work right now, which is why I couldn't put it in the original post, but if I have a chance to I'll post it this evening.

 

[VirtualLarry]

If it's a crappy generic, then yes, if you care about your PC, you would buy a better brand-name PSU to go in it.

 

[laserhawk64]

My first, best, and only self-made computer has an Allied 300w in it, and if I cared about it any more I'd probably start calling it "my baby"...

 

[Absolution75]

eh

You can regularly get decent psu's for $20 after rebate in the 400-450 watt range. It should be fairly common sense to grab one of those rather than have a garbage psu destroy your pc.

 

[KCfromNC]

Anandtech's review of the 4670 using a qx9770 showed the system under load drew about 140W at the wall. Scale that @ 80% efficiency = 115W. Your CPU uses half the power of the review system, and the 4650 is a slower card so it also uses less power.

Short version - even if the crappy PSU is out of spec by 50%, you still have 50% headroom to work with.

 

[Eluros]

Anandtech's review of the 4670 using a qx9770 showed the system under load drew about 140W at the wall. Scale that @ 80% efficiency = 115W. Your CPU uses half the power of the review system, and the 4650 is a slower card so it also uses less power.

Short version - even if the crappy PSU is out of spec by 50%, you still have 50% headroom to work with.

That's a very helpful response-- you gave me a technical justification for your argument. Thanks!

 

[veri745]

Anandtech's review of the 4670 using a qx9770 showed the system under load drew about 140W at the wall. Scale that @ 80% efficiency = 115W. Your CPU uses half the power of the review system, and the 4650 is a slower card so it also uses less power.

Short version - even if the crappy PSU is out of spec by 50%, you still have 50% headroom to work with.

You're actually scaling that the wrong way. 140W at the wall means the actual system is only drawing 112W assuming 80% efficiency

 

[KCfromNC]

You're actually scaling that the wrong way. 140W at the wall means the actual system is only drawing 112W assuming 80% efficiency

I think you're saying exactly what I did in my response (other than rounding from 112 to 115W - which doesn't matter because 80% is also a guess). Am I misunderstanding ?

 

[tomoyo]

The real danger to me, a crappy psu might destroy your whole system. Losing a computer is far more important than buying a good psu.
Why do I see so many people who seem to think losing a whole computer is somehow not a major threat?

 

[Termie]

You won't need 6-pin PCIe connectors for the HD4650, and the e8400 is very efficient at load. Your whole machine when loaded with HTPC tasks probably won't go over 100 watts. I have a similar setup that idles at 72 watts and rarely breaks 100.

You're fine. I don't care if your PSU is junky - it can handle 100 watts.

I should note, however, that to connect your SATA hard drive, you'll need a SATA power plug. You might need an adapter for that if that PSU really only has molex.

 

[veri745]

I think you're saying exactly what I did in my response (other than rounding from 112 to 115W - which doesn't matter because 80% is also a guess). Am I misunderstanding ?

I must be losing my mind, you sure you didn't ninja edit your first post from saying 175W?

 

[Joseph F]

I think it depends on what version of ATX it's certified for. If it's certified for a new-ish version of ATX12V then you shouldn't worry about it too much. But since you said it only has molex connectors then it's probably an older version of ATX and should probably be used in an older rig than what you have.

 

[Termie]

I think it depends on what version of ATX it's certified for. If it's certified for a new-ish version of ATX12V then you shouldn't worry about it too much. But since you said it only has molex connectors then it's probably an older version of ATX and should probably be used in an older rig than what you have.

Ok, I've changed my mind too. This sounds like not just a crappy PSU, but a really, really old one. If it doesn't have any SATA power connectors, just junk it, and get this Corsair:

http://www.newegg.com/Product/Produc...9017&Tpk=cx430

Currently $17(!) after rebate and code: BTEZZZS23

No reason to spend time worrying about this when a decent, and more importantly, modern PSU is so cheap.

 

[tomoyo]

Wow $18. I wonder if corsair can even make money at those prices. I guess this shows what corsair was trying to compete for, because I'd take a CX430 over any crap psu for sure.

 

[TemjinGold]

Ok, I've changed my mind too. This sounds like not just a crappy PSU, but a really, really old one. If it doesn't have any SATA power connectors, just junk it, and get this Corsair:

http://www.newegg.com/Product/Produc...9017&Tpk=cx430

Currently $17(!) after rebate and code: BTEZZZS23

No reason to spend time worrying about this when a decent, and more importantly, modern PSU is so cheap.

Agreed. For the price of a cheap dinner, you won't have to find out whether your old psu will kill your pc or not.

 

[veri745]

Ok, I've changed my mind too. This sounds like not just a crappy PSU, but a really, really old one. If it doesn't have any SATA power connectors, just junk it, and get this Corsair:

http://www.newegg.com/Product/Produc...9017&Tpk=cx430

Currently $17(!) after rebate and code: BTEZZZS23

No reason to spend time worrying about this when a decent, and more importantly, modern PSU is so cheap.

Agreed, the CX430 isn't quite the gem that the CX400 was, but it's the best you'll find anywhere near that price.

 

[tomoyo]

Honestly I feel like if you can't even afford a psu, why are you buying computer parts?