Though Crossfire is real fun and a very fast way to quickly get more performance, it also effectively adds more 'load' on your power bill. Example each added 4870 card can consume up-to 175 Watts per card when 100% stressed.
Typically this number is lower as your GPU in a lot of situation will not reach that TPD (wattage peak). On average we expect a 150 Watt power draw during gaming, per card.
We'll now show you a bunch of tests we have done on overall power consumption of the PC. Looking at it from a performance versus wattage point of view.
The methodology is simple: We have a device constantly monitoring the power draw from the PC. After we have run all our tests and benchmarks we look at the recorded maximum peak; and that's the bulls-eye you need to observe as the power peak is extremely important. Bear in mind that you are not looking at the power consumption of the graphics card, but the consumption of the entire PC.
Our test system contains a Core 2 Duo E8400 Processor@ 3.0 GHz (FSB 1333), the ASUS P5E3 DeLUXE mainboard, stock cooling on the CPU, DVD-rom and a WD Raptor drive. The results:
System Under load
Radeon HD 2900 XT
Radeon HD 4850
Radeon HD 4870
Radeon HD 4850 Crossfire (2)
Radeon HD 4870 Crossfire (2)
The monitoring device is reporting a maximum system wattage peak at 480 Watts with 2-way 4870 Crossfire. So with 3-way 4870 CrossfireX that number would be 620-650 Watts. Very scary stuff to be honest.
Heat levels - Be Warned
Typically both the Radeon HD 4850 & 4870 will get very hot. 80-90 degrees C temperatures for these GPUs are pretty normal. The problem with the 4850 is that this heat will be dumped inside your PC. The positive fact about the 4850 is that it is a single slot cooler. Airflow to the cooler is pretty good, though things change when you add a second or even third card as the cards are stacked quite close together and are dumping air inside your case. [Ed - Excellent airflow is required here, or a change of cooling solution]
The positive thing about the dual-slot 4870 is that heat is dumped outside the PC. The downside, the double sized cooler. Two or three next to each other requires you to have a very properly cooled down chassis as there is very little space in-between the cards.
The 4870 cards have very little room for proper air-flow, while the air intake is located on the side.
Bear it in mind. For the GPU itself, this heat level is not an issue. In fact a GPU can reach 120 Degrees C before the fuses blow. Yet you need to be aware of the fact that the cards require a constant supply of air-flow in order to keep them from heating up too much.
Please make sure you have a very well ventilated PC.
With that in mind .. let's start some games and see how well they perform.
Hardware and Software Used
Now we begin the benchmark portion of this article, but first let me show you our test system plus the software we used.
ASUS P5E3 DeLUXE mainboard
Core 2 Duo E8400 Processor@ 3.0 GHz (FSB 1333)
Various Radeon HD 4800 series Various GeForce GTX 200 series
2048 MB (2x1024MB) DDR3 1333 MHz Corsair
Power Supply Unit
Enermax Galaxy 1000 Watt PSU
Dell 3007WFP - up-to 2560x1600
OS related Software
Windows Vista 32-bit DirectX 9/10 End User Runtime AT Catalyst Press BETA 8.6 driver & Final 8.6 hotfix NVIDIA ForceWare 177.34 NVIDIA nForce 590/680i platform driver 9.53
What are we looking for in gaming performance wise? First off, obviously Guru3D tends to think that all games should be played at the best image quality (IQ) possible. There's a dilemma though, IQ often interferes with the performance of a graphics card. We measure this in FPS, the number of frames a graphics card can render per second, the higher it is the more fluently your game will display itself.
A game's frames per second (FPS) is a measured average of a series of tests. That test often is a time demo, a recorded part of the game which is a 1:1 representation of the actual game and its gameplay experience. After forcing the same image quality settings; this time-demo is then used for all graphics cards so that the actual measuring is as objective as can be.
Frames per second
very limited gameplay
average yet very playable
best possible gameplay
So if a graphics card barely manages less than 30 FPS, then the game is not very playable, we want to avoid that at all cost.
With 30 FPS up-to roughly 40 FPS you'll be very able to play the game with perhaps a tiny stutter at certain graphically intensive parts. Overall a very enjoyable experience. Match the best possible resolution to this result and you'll have the best possible rendering quality versus resolution, hey you want both of them to be as high as possible.
When a graphics card is doing 60 FPS on average or higher then you can rest assured that the game will likely play extremely smoothly at every point in the game, turn on every possible in-game IQ setting.
Over 100 FPS? You have either a MONSTER of graphics card or a very old game.
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