Note/Advice/Tips/Guide to those who going to buy graphic cards.
I was fooled by some other fool/fools who designed graphic cards.
2 types of card design i see & i call it OPEN type & CLOSED type. I don't know what manufactures use to call.
Example for OPEN type card is R6970 Lightning card.http://www.msi.com/product/vga/R6970-Lightning.html
Example for CLOSED type card is MSI R6970-2PM2D2GD5 card.http://www.msi.com/product/vga/R6970-2PM2D2GD5.html
I bought 4 nos. of OPEN type, R6970 Lightning, since it is factory over clocked to 940Mhz & also has TWO FANS.
I thought since it has TWO FANS & ITS MILITARY DESIGN, it will run much cooler than the other type.
But i was WRONG.
Actually this is foolish design to use in a multi GPU card setup. This type of cards MUST NOT be used if more than 2 cards in a pc.
In my mining setup, 6 cards are connected from slot1 to slot6 using riser cables, with more than 1 inch gap between each cards.
The LAST card in slot 6 , grabs air from open, while the card before that grabs air from back of last card & it goes on.....with FIRST card getting air from back of second card.
Here comes the problem.
The last card runs cooler(65C) & the FIRST card runs HOTTER than all (>95C)
What happens here is the last card grabs air from outside & the card design allows air to come out of the card in ALL directions.
If you look at the card, you can see there is gap in ALL 4 sides of the card for the air to escape.
The fan grabs air, pushes to the heat sink & the hot air escapes from all sides.
The card before the last card, grabs the HOT air from last card, & gets temperature increased & air escapes through all sides.
As this goes on, the FIRST card gets hottest air & so the temperature of the card is very high.
Placing 6 120mm fans on top of cards don't reduce much temperature. Only up to 85C.
Here CLOSED type works better.
In closed type air is sucked from mouth of the card & it passes to the GPU & comes out of the ass(back) of the card.
Their is NO GAP for the air to escape in any side.
This makes the air coming out of card is VERY hot. But it cools the GPU.
Since it SUCKS air, even in multi card setup, it doesn't increase the heat of near by card, since the air never escapes on sides.
Air goes out only on cards ass.
But this type also has another problem.
Since it sucks air from mouth & release hot air through ass & NO GAP for air to escape in any side, DUST if accumulated on the ass will NOT allow the hot air to go out easily.
So, it needs to be looked in to every now & then to keep the ass clean.
If not the hot air will fry the GPU & you get BAD smell.
Any one object this or has some other experiences can share.
I want to know the pros & cons of the different design, so if i buy cards in future it must be a correct one.