2x7990 or 4x7970

[Hash-IT]

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 ?