2x7990 or 4x7970
#11
you will need a lot more than 1000W of power. you should budget at least 1200W RMS to power the GPUs alone, so i would recommend going with a 1500W or 1600W 80plus Gold or Platinum-certified power supply.

by 'reference design' i mean the design developed by AMD, not one with a third-party cooling solution.

these are all reference design cards:

http://www.newegg.com/Product/Product.as...6814103201
http://www.newegg.com/Product/Product.as...6814161399
http://www.newegg.com/Product/Product.as...6814127652
http://www.newegg.com/Product/Product.as...6814129204

anything that doesn't look like that, like the ones that have two fans on the side, should be avoided.
#12
Why reference design? What are their advantages to this model with 3 fans, for example:
"GIGABYTE GV-R797OC-3GD Radeon HD 7970 3GB 384-bit GDDR5 PCI Express 3.0 x16 HDCP Ready CrossFireX Support Video Card"
http://www.newegg.com/Product/Product.as...6814125413

I do not argue, just choose the parts responsibly.
#13
reference design cards have enclosed shrouds with a single centrifugal fan, which forces the hot exhaust air out the rear of the card and completely out of the case.

non-reference design cards have open shrouds and push the air upward/downward, keeping the hot air inside the chassis and creating turbulence with your chassis fans. for this reason, non-reference cards are best used in open-air chassis.

reference cards are usually over-engineered a bit, with the intention of building a quality, stable platform so a reference design card gives you some assurance as far as quality control.

non-reference cards are usually cheaper than reference cards because they do not receive the same level of R&D or testing as the reference card. they typically also lack circuity for things like voltage control, as it adds to the price of the card. they also historically have less overclocking potential than the reference design cards.
#14
(02-07-2013, 12:52 PM)epixoip Wrote: reference design cards have enclosed shrouds with a single centrifugal fan, which forces the hot exhaust air out the rear of the card and completely out of the case.

non-reference design cards have open shrouds and push the air upward/downward, keeping the hot air inside the chassis and creating turbulence with your chassis fans. for this reason, non-reference cards are best used in open-air chassis.

reference cards are usually over-engineered a bit, with the intention of building a quality, stable platform so a reference design card gives you some assurance as far as quality control.

non-reference cards are usually cheaper than reference cards because they do not receive the same level of R&D or testing as the reference card. they typically also lack circuity for things like voltage control, as it adds to the price of the card. they also historically have less overclocking potential than the reference design cards.

All this is very interesting, thank you.

Can I ask how the average guy would know what is a reference design ?

Those cards don't mention it in their title, I understand you say to look for the single fan but my reason for asking was how we would know for other models in future without having to keep asking you ?
#15
The reference design has been visually the same for the last 5+ years. If it changes I'm sure it will be adequately discussed.

In the mean time, check out those Newegg links I posted above. The reference design will have a sturdy, solid shroud that completely encloses the face of the card, with a single axial centrifugal fan at the rear of the card (or, in the case of the 6990, in the middle of the card.)
#16
Actually, i just thought of a pretty good way to determine what the reference design looks like: just go to AMD's website and look at the picture of the card :]

http://www.amd.com/us/products/desktop/g...-7970.aspx

The picture on the site will *always* be the reference design.
#17
Thank you epixoip

I didn't think it would be as simple as just comparing what it looked like, (physical appearance). I thought there would be a more technical method.

I will always compare to the original image on the AMD site from now on ,thanks.
#18
yeah, they're real easy to spot. the reference cards are all identical, with the exception of the brand name on the face of the card. we have a box that has reference design 7970s from three different vendors, and from the top you cannot tell which is which.
#19
(02-07-2013, 02:36 PM)epixoip Wrote: we have a box that has reference design 7970s from three different vendors,

I am so overcome with jealousy I cannot reply to this thread any more.


Big Grin
#20
I agree with epixoip, if they are all in a case, for sure reference design but even then, I have found that the middle cards still get "cooked" because they are in the middle and cannot get any airflow due to the other cards being right next to them and the heat radiates out of the cards. The reference coolers do get most of the heat out of the front of the cards but not all of it.

See how u go but have a serious think about cooling and maybe doing a custom mod on your case IF they over-heat too easy.
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