The new commander of the Red Army is equipped with two Cayman GPUs (VLIW4) on the same PCB, with 830MHz core clock is the same default 1250MHz memory clock (equivalent pulse 5GHz effective). Each GPU has 256-bit bus interface to 2GB of memory (like the HD 6970), bringing the total capacity of the HD 6990 GDDR5 memory up to 4GB
The case of 5970, the limits of physics and electricity that AMD had to cut “a little” my little pet. The result is a card with a lower parameter 5870 version pretty much single-core: 125MHz core clock is reduced while also lower memory clock to 200MHz (800MHz effective). With such inferior human impulse, the strength of the 5970 equivalent 5850 CrossFire (CF).
A similar problem occurs for the HD 6990 but at a lesser level. Default 830MHz core clock rate of 50MHz low only 6990 (5.5%) compared to 6970, while the effective memory clock to 500MHz decreased (9%). In addition, each GPU Cayman are well equipped 1536 SP and 32 ROP, making the HD 6990 can be seen as two complete version when it is capable of overclocking slightly to HD 6970’s 880MHz default.
Management mode of new energy helps power consumption of the card in Idle mode drops to 37W – only equivalent (or even lower) any natural person who single graphics card. But when the working mode Full-load, the HD 6990 requires providers to 375W This is also the limit of the PCIe slot power supply (75W) and two 8-pin power supply (150W x 2) that any graphics card face. However, as noted above HD 6990 overclocking still slightly to 880MHz. Surely AMD’s engineers have found a way to overcome this limitation.
One of the factors leading concern of the new generation of graphics cards is power consumption. Equipped with 2 top 8-pin auxiliary power supply, can guess that the maximum power consumption of the card is 375W. As noted above, this is the threshold that any graphics card also face (unless designed to add extra power supply first Tuesday). As in the case of the HD 5970, any additional demands for power are increasing pressure on the PCIe slot. This requires that the supplies have to be very good and stable motherboard.
At the default clock, voltage of 6990 decreased slightly from 6970 to 1,12v to meet limits on power. AMD has had to sift out the best Cayman chips to run stable at 830MHz with voltage pulses smaller.
Before going further, let us together agreed on the concept of power consumption (TDP). Here is the definition: TDP – Thermal Design Power – is the amount of heat that the cooling system should be cleared. Power consumption must be less than or equal to this level.
Thus, the TDP is the device emits heat during operation (the unit is W), this heat energy equivalent to the power consumption of the device. So we usually understand the meaning TDP power consumption. In the rest of the article, we need to understand this index in both meanings.
Returning to the issue, by reducing the voltage pulse and the GPU, AMD has maintained the card’s stop threshold TDP 375W . However, with a little trick that AMD technology called PowerTune, HD 6990 also has the ability to increase overclocking performance a little bit more.
PowerTune be officially introduced for the first time on January 12/2010 6900 series, but in fact this technology has been tested on HD 5870 AMD before. We already know that the TDP is heat generation during the operation card, namely gaming, watching movies … The magnitude of its continuously variable depending on application requirements or the severity graphics and relies primarily on the core clock, memory clock and GPU-Load (operating condition or the severity of the GPU, a value between 0 -> 100%).
In scenes heavy game requires high graphics processor with multiple effects such as fire, shadows and light …, graphics cards to work hard, GPU-Load rising, meaning more heat radiating. In contrast, in the light scenes, heat generation is much less. In the same game, has not always been the graphics card also squeeze.
Based on the fact that, both AMD Nvidia are given an idea and apply them in practice: TDP pose safety threshold for the card, if you pass this threshold, the driver immediately reduce power / pulse. That way, we can comfortably overclock, enjoy a little extra performance when needed. If you exceed the limit, PowerTune handle.
The hardest part is finding the balance pulse. If too greedy, the card will constantly overheat resulting in reduced pulse continuously to normal levels; while too cautious shy also prevent you from enjoying the highest possible performance.
FurMark is software enthusiasts very popular graphics cards, is dedicated to the highest temperature determined by exhausting graphics cards for a long time. For HD 6990, has been playing cheat PowerTune humbled by continuous pulse every time the temperature rises too high. We can see this application has forced the card to reduce how terrible impulse. Meanwhile, in the game Metro 2033 but also occurs to a lesser extent.
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With a common set PowerTune is +/- 20%, the HD 6990 will have TDP identified in 300 -> 450W.
After power consumption, while other issues are also a concern: the compatibility of the application with CrossFire technology. What happens if a game (or game mode) does not support this technology? At that time only one GPU will work. Results for our poor performance than single-core solution 6970, by each GPU had been reduced pulse little. Hopefully in the future there will be a similar technology that Intel’s Turbo Boost apply in such cases: automatically increase the GPU clock if there is a break. That will help users reduce disadvantage when facing applications “do not play with CrossFire” windowed mode like the game, application modeling, GPGPU, or the game does not support CrossFire.
Like 5970 and 5870 2GB, 6990 is also equipped with 16 RAM chips – 8 for each GPU. One of the differences of 6990 compared to 6970 is the only pulse 5GHz GDDR5 memory instead of GDDR5 6GHz as mononuclear version (template Hynix T2C memory usage). The reason again encapsulated in four words: power consumption. 6GHz 1,6v RAM voltage requirements while for 5GHz is only 1.5V RAM. From this fact can make judgments that memory overclocking capability for 6990 is not much.
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