Legit Reviews

on newegg, most 3870 X2's say they need a 550W PSU with two PCIe 6pin connectors, except the one Diamond card that says it needs a 450W PSU with only one PCIe connector, execpt in crossfirex, with which it needs a 550W.

anyway, i went on PSU calc lite and with my entire system(not the one in my sig by any means) @ 100% CPU TDP, and 95% total system utilization, and two 3870's in crossfire(the 3870 X2 is not in the PSU lite menu) it says i need a 435 Watter

i may be confused, but what Wattage PSU do i NEED, and how many connectors?

btw, i have a 450W PSU(i know, i'm borderline either way) and have one PCIe connector(unless ken is shipping one also, in which case i will have two(they are both molex-PCIe converter cables)(but i would like have the second for something else))

diamond is wrong cause the card has two PCIe power headers on it... one 8-pin and one 6-pin... I'd get 500W+ personally.

and not a coolmax PSU

i was under the impression that the 6 pin was for basic operation, and the 8 pin was for overclocking(btw, what IS a 8 pin connector?)

keeping in mind that, well, i cant afford a new PSU right now, and if i CANNOT, CANNOT use the 3870, i can use my x850XT till i can, and have the 3870X2 sit on my desk, instead of the 850(and no one wants to see that happen)

The 3870 X2 makes a very nice paperweight I hear.

ibleet wrote:The 3870 X2 makes a very nice paperweight I hear.

thats not really what i wanted to hear

what about PSU calculator, it says i only need 435W, with stuff above the "recommended"(at 100%), and i also dont HAVE to OC the CPU by 650MHz, when i OC 250MHz,it says 417W, so with the added 30 Watts (because the X2 actually uses 30Watts more than 3870s in crossfire) its at 447(keeping in mind PSU calc overestimates)

I think the big thing is that everyone here would hate to see you fry an awesome GPU because it was paired with a el cheapo Coolmax PSU. In the end, it's really your decision but as far as the question of should you push your current PSU, well, 'signs point to NO!'

Me personally, I'd go with the advice of the crazy frog and the muppet, get a new PSU first.

When I was in a hurt for parts money I'd Ebay up, rake leaves, yard sale. You'd be amazed at how short a time it takes to drag up enough cash. Depending where you live, given the moniker "skierkid" pray for snow and shovel shovel shovel.

I think the issue that would be of the biggest concern is that many sub 500W PSUs are of questionable quality which translates into them not having a STABLE flow of juice at the level they claim. I have read lots of PSU reviews by Jonny Guru and others and a major problem is that they will say 430W but only put out actual 350 or less in some cases. All the better PSUs are 500W or higher and they actually put out what they are rated at. IF you can find a really good quality PSU that is under 500W you MAY be ok with a 400+W but you are not likely to find one. I looked for a long time because I was in your situation, minus the sweet video card on my desk, of needing a new PSU that could do what I needed. I could not find a review anywhere on a sub 500W PSU that gave me any confidence at all until finally my old POS blew out in a thunderstorm forcing me to buy a new PSU. Now that I have my Corsair I wish I had done it a long time ago. NOw I feel all fuzzy and warm knowing for sure that my PSU is up to the task for a while to come and I don't have to worry about power when I plan my next upgrade.

I REALLY hate to say it especially since I got a little touchy with Diceman ( sorry Dice you were right!) a year or more ago for telling me what I am about to tell you. Mow some grass shovel some snow e-bay it, whatever you have to do ( no soul selling please) but get a good solid PSU to wrap your new sweet build around I personally guarantee you would will forever be glad you did.

I'll send you a PCIe power cable.

You should get a 500W+ PSU. You're right, you don't need a 8pin connector, you only need that for overclocking via the ATI overdrive option in the control panel.
Infact you can OC that card if your just using 2x 6pin cables, you just need to have a quality power supply.

The 8pin cable only adds two more ground wires, no extra power!
If your PSU is good, then the cables would be good quality and can cope with the extra current draw, even with just 6pins.

You need a GOOD PSU as you're essentially running Xfire.

could i get a cheaper brand(ie. rosewill) if i go higher power(600W)

This or This

skierkid450 wrote:could i get a cheaper brand(ie. rosewill) if i go higher power(600W)

This or This

Typically NO...Its a myth that more wattage is better, or even necessary in most cases. Most important is the amps and stability of the 12v rails in relation to what is required by your hardware. More wattage does not make up for instability and required amps.

For example, a Corsair 620hx is superior to a POS 1000w PSU. And the Corsair has 2 PCI-E 6 pin connectors with modular cabling.

One thing I have learned from LR is to never cheap out on the PSU as it may cost you much more later on when it takes a dump and other parts go along for the ride.

A great lesson to learn when you're young is to exercise a bit of patience and work hard for what you want. In the end its all the more sweeter.

This is not a plug but Jonny Guru has about 60 very thurough PSU reviews on his site. I would look those over good before I did anything. Ultra brand has some good PSUs for lower cost but be VERY careful.

http://jonnyguru.com/modules.php?name=N ... y4&reid=32 - it got a 8.5 in performance(Rosewill 500w) and the Rosewill 600W ones have 19A on both 12v rails(rated at least) and its in the same series as the reviewed

If you can make sure that the two separate PCIe connectors going into the GPU come from the two separate 12v rails, that *should* work.

How is your case for ventilation?

You should know that the minimum power supply certified for crossfire (essentially that card) by ati.amd is a 670W PSU...

Dan

DMB2000uk wrote:If you can make sure that the two separate PCIe connectors going into the GPU come from the two separate 12v rails, that *should* work.

How is your case for ventilation?

You should know that the minimum power supply certified for crossfire (essentially that card) by ati.amd is a 670W PSU...

Dan

1. how would i do that
2. its my avatar, two side fans, one rear, one front(all 80mm )and my vid card PCB(abient temps basically) stays at 31-35C most of the time when CPU and GPU are around 40-48C
3.whats certified is not really on my mind

Some PSU makers include a 'pin out' of the PSU that tell you which wires are from which rails, if it's not in the manual (or somewhere online) then it is a bit hard to find out.

3870 Xfire uses 30w less than the 3870X2 (as you are aware). According to "the truth about graphics hardware requirements" 3870 Xfire uses 193W at peak. So the 3870X2 will use 223W at peak. This being all on the 12v rail puts it's needed amps at 18.58A.

With choosing a PSU with 19A on the 12v rails, It's for this reason that you need to be able to split the load of the card across more than one rail. I guess its also for this reason that ATI.AMD only have certified high power PSUs, they probably have their own power rail just for PCIe stuff.

The jonnyguru review says that the PSU is only good if you can keep it cool, I should have thought that your case ventilation is ok for it. Out of these two you should go for the 600w version of that rosewill to be on the safe side.

Dan

DMB2000uk wrote:The jonnyguru review says that the PSU is only good if you can keep it cool, I should have thought that your case ventilation is ok for it. Out of these two you should go for the 600w version of that rosewill to be on the safe side.

Dan

thats the only one i was considering(one of two 600W by rosewill)(assuming its price doesnt go way up by the time i buy)

Rosewill PSU's are tier5 and on the "not recommended" list here.

Official Tiered psu Listing

Do yourself a favor and choose at least a tier2 PSU.

Read my post above in case you missed or ignored it.

But did you read the jonnyguru review?

Dan