Possible Airflow Problems with 4870, VX450w and XQPack2

Wizlah

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I've had a 4870 about two weeks now - the xpertvision/palit dual model - fitted quite tightly into my XQPack2. the card is fine and I got it at an excellent price, but one thing various comments and articles mentioned about it was that it doesn't vent air out the back of the case, in part because it doesn't have a plastic shroud like the standard 4870. The two fans do a fine job of keeping it cool (albeit noisy and I'm thinking about replacing them at some point), but the hot air vents into the side of the case, and there's very little clearance to the PSU above. The PSU is a Corsair VX450w. I know that it is recommend to use a 500w PSU, but I figured the corsair would cope fine because it is meant to very efficient and I've not seen any reviews of system configurations with a 4870 in it where the power consumption goes over 370w .

This evening I started to notice a smell like burning whilst I was gaming (nothing too demanding - just Rome Total War), so shut down the pc quickly, popped the case and too a look. the heatsink on the card was very hot, and I wondered whether the problem might have been the PSU fan taking in hot air from the card below and causing problems? I wondered turning the PSU upside down and drilling some holes in the top of the case made sense - pulling in cooler air from outside. Any other ideas what it might be?

The rest of the system is as follows:

Gigabyte MA78GM-S2H mobo
4 gig ddr2 corsair ram
Athlon 5000 Black EDition CPU.
Samsung 250gb Spinpoint F1
Samusng DVD Drive
Silverstone SST-MFP51B remote control/LCD display.
 
My friend smelled that burning smell, and very shortly after (one more boot up, within 15 seconds) his PSU took a nosedive and took his motherboard, processor, and hard drives out. Maybe some other stuff, we didn't test it.

There was also a loud capacitor sound as well, so if you're not hearing that it could be something else. When the PSU actually died, there was some popping.
 
No popping sound. I took the precaution of flipping it upside down for now and leaving the case off. watched a recorded ts file with it and that seemed to do fine - about an hours worth of television. just wondered if pulling in hot air might be causing the problem. or whether I am in fact overloading the PSU.
 
Overload will cause it, the Corsair's fan will spin up noticeably to compensate for temps.

PSU is generally 80% efficient, so the math is 450w = 360w efficient load.
 
Yeah if it is working better with the cooler temperature, you may be skirting the limits of your power supply. Cooler power supplies are more efficient than hotter ones, if what I heard from quite a few people is correct. I'd work on getting a more powerful one because when they go they can take a lot out, and overloading them is not good either.

I got my 700W for this reason (well and mostly because it was on sale for what most 500W ones were going for at the time, and it has a huge 135mm fan on it which helps out in my case).
 
The corsair should shut down in the case of overload, but the more I look at it, the more I'm kicking myself. Reading about, I've not given myself much if any headroom for overclocking, and the xtreme outervision power calculator suggests I'm sitting on the cusp. I'm pretty sure the 4870 amp requirements are covered by the VX 12v rail. But it had been a while since I did my build, so when I saw the good price on the 4870, I jumped on it quickly because palit/xpertvision's build generally seems to be very solid and the dual bios thing might be something I'd fiddle around with (to reiterate - I got this about £20 cheaper than I would normally get a reference pcb 4870 - www.ginger6.co.uk). I totally forgot to check the PSU in my SFF build and was pretty sure I'd stuck a 550W in there to be on the safe side.

I'm not messing about. I'll just get a VX550 today or maybe jump up to a 600w+ psu. It's not great - the 4870 was the last thing I was planning on spending money on for a while, especially in these troubled times. And I still reckon I could do with a bit of dremel work on the case just to get more airflow and cooling sorted on it. Damn - if they became available in the UK I was thinking I might stretch to one of those fancy new 790x matx mobos that I hear DFI are doing. Guess that will have to wait.
 
The VX 450 is fine for your setup, Corsair even recommends the VX450 for 4870 setups with Dualcores. The issue you might have is that since you're using a 4870 with the non 'dustblower' design that normally leads alot of heat out of the case.. now your PSU is sucking up that heated air and getting even hotter. An hot PSU is even less efficient than a well cooled one which in turn generates even more heat.

So my 5 cents, check temps on videocard when playing, put hand behind the PSU's blowout and check if the air is overly hot.
 
Considering he smelled something burning, the last thing you should be suggesting is keeping the PSU.
 
pulled the 4870 for the moment, and tested the psu with a basic led tester. It seems fine - i was getting a readout on all the various connectors. I think the hot air is an issue - this is only the second time I was gaming for longer than an hour (this was a two hour session), and I think that it can't have been helping matters.

But the whole episode has highlighted to me that I don't have very much headroom for things like overclocking, so I should probably look at upgrading on that basis alone. I'm also wondering whether the two sockets required by the video card were causing a problem - obviously the PCI-E plug is pluged into one, but I had to use the adaptor to plug another of the 4 pin peripherals into the card - and I'm not clear whether that was overloading the max amp load on the PSU
 
Considering he smelled something burning, the last thing you should be suggesting is keeping the PSU.

Electronics can give off odd smells when they're running very hot. The PSU is 100% Adequate for his setup so the explaination is most likely that it's running too hot and is causing the smell due to high heat.

Mind you the Corsair VX450 have Capacitors rated at 105*C and a fully working protection in case of overload. The PSU is most likely fine unless it was broken to begin with.
 
Overload will cause it, the Corsair's fan will spin up noticeably to compensate for temps.

PSU is generally 80% efficient, so the math is 450w = 360w efficient load.

No the math is 450W supplied = 562.5W consumed at the wall.
 
QPacks are not known for their awesome air flow, and the non reference design video card would probably fare better in a roomy tower as opposed to a cramped shoebox. I would recommend either a case with horizontal side vents next to the video card (mod your own maybe ?) or a card with a heat sink / fan combo that exhausts (again, if you r e feeling creative... fabricate some kind of shroud).
 
No the math is 450W supplied = 562.5W consumed at the wall.

Dunno about the wall part, but a PSU isn't 100% efficient, meaning it doesn't supply the complete amount of power advertised.

Can kinda see it here:
http://www.anandtech.com/casecoolingpsus/showdoc.aspx?i=3413&p=6

There's always a loss when converting something to something else, e.g. drivetrain loss. That labels are there - 80+ certified = can attain a minimum of 80% of the advertised number, then there's silver which is 90%?.
 
Okay, so there may be two problems. One is definitely hot air, and the other is the possibility that the PSU is not coping with 4870 and everything else.

The first I can address, and I'm willing to experiment since I think the case could already do with some more airholes, and also getting some new tools and some material is deffo cheaper than getting a new PSU if I don't need it. the one question I'd ask there is if I were to make a shroud, what kind of material would people recommend to make it with? Any old plastic bits and bobs? any materials that you think I should avoid?

Moving onto the powersupply coping - I did check corsair's tool for 'which power supply is right for me' and even if you tick boxes for extremely overclocked cpu and overclocked card, it still says you can use a VX450. I'm willing to believe that but two things have me bugged.

1) minimum amp requirement for the 4870 seems to be anywhere between 32 and 36 on the 12v rail, from anything I've read online (I can't find an exact spec listed on the amd/ati website). Max load on the vx450 12v rail is 33A. Surely the card itself isn't using 32-36amps?

2) this is where I get confused on power supplies - if I plug a molex adaptor for the second 6 pin plug onto one of the 4 pin peripheral adaptors, is that putting too much load on the PSU?

I think I'll go ahead and mod the case, but how do I test how the PSU is coping with providing power for the system?
 
Stability is where you will see the PSU's performance. Things crash, strange stuff happen, crop circles pop up in your carpet - can be due to PSU inefficiency.. or driver and whatnot problems.
 
Let us get this straight, say for instance that the card is drawing almost all of it's power from the SINGLE 12V rail it has. now say that the card is pulling a hefty 200W (that's pretty overkill) load of the 12V rail. Now basic math tells us that this 200W load on the 12V rail measures up to... 16.5 amperes. That means we got a wooping 10 Amps left if we want 6.5 amps of room to spare. Theese 10 amps equals about 120W of power on 12V Alone!

And as we all know systems use other rails than 12V as well, so yes, even if you pulled ALL the power of an intel quadcore with a 4870 (roughly 350W total) of only the 12V rail it would not even break the 12V rail supply. Luckily theese components use the other rails as well, not just the 12V.

Your PSU is totaly adequate for the system unless it's faulty, but do remember that as temps increase the PSU gets a harder time working at full power. An overheated 450W supply might not be able to supply more than 400W before getting overworked even if it's a top quality unit. No need to say that his applied to ALL Power Supply Units, I would not recommend sticking ANY psu in an overheated position due to how it affects them.
 
Just an update on this. Following on rokk's comprehensive math, and my own suspicion that this was more about hot air going into the PSU than any innate problems, I decided to avoid any new purchase and just drilled a set of holes in a starburst arrangement in the top of the case, and turned the PSU around so it was pulling in air from outside. It does not know seem to be exhausting any hot air, although the PSU grill and the case in general still seem to get very warm (presumably because the hot air from the card that isn't venting is heating up both the casing of the PSU and the aluminium of the case. I'll need to drill more airholes in the side of the case, or put in slots. Over to the case modding forum for me . . .

I just wanted to post this in part as a reminder that sometimes the solution isn't more expensive components! Thanks to everyone for their posts.
 
You should be fine, I built similar computer but with 8800GTS G92 and the temps were really good.
 
Happy to be of help, hope it works out for you!
As long as the temps are kept in check and the PSU is not exhausting overly heated air, all is fine.
 
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