AMD Radeon HD 6990 and Nvidia GeForce GTX 590
PCB Design and Functionality
I've got reference samples of both cards without any packaging and accessories. So, let's take a look at them right now.
The AMD Radeon HD 6990 is as long as 305 millimeters, making it incompatible with quite a few system cases. Its height and depth are 101 and 40 millimeters, respectively. The Nvidia GeForce GTX 590 is smaller at 280x99x35 millimeters, so it can be installed into more system cases. Besides, the new card from Nvidia is somewhat lighter (1038 as opposed to 1139 grams). The face side of each card is covered with a plastic casing with a blower (HD 6990) or an axial fan (GTX 590).
The reverse side of the Radeon HD 6990 is covered with an aluminum plate except for the spots opposite the GPUs. The GeForce GTX 590, on the contrary, has such plates opposite the GPUs only whereas the middle part of the PCB is bare.
The cards differ in their connectivity options. The AMD Radeon HD 6990 has four mini-DisplayPorts and one DVI output whereas the Nvidia GeForce GTX 590 features three DVI outputs and one mini-DisplayPort.
There is a vent grid in each card’s mounting bracket for exhausting the hot air, yet some of that air remains inside the system case anyway.
Each card has two 8-pin power connectors at the top of the PCB.
They do not differ much in terms of the peak power draw: 375 watts for the Radeon HD 6990 and 365 watts for the GeForce GTX 590. AMD recommends a 750W or higher power supply with two 150W power connectors for its graphics cards. A 1200W or higher power supply is recommended for a CrossFireX tandem built out of two Radeon HD 6990s. Nvidia has the following recommendations: 700 and 1000-watt power supplies for a single GeForce GTX 590 and a SLI tandem, respectively.
Each card has a single connector for building multi-GPU configurations. It is located in the top front part of the PCB.
There is a small switch next to the CrossFireX connector on the Radeon HD 6990. Instead of switching between the main and backup BIOSes as is implemented in the Radeon HD 6970 and HD 6950, this switch selects the operation mode of the card's GPU. When turned on, it increases the GPU clock rate by 50 MHz. The GeForce GTX 590 has no such switch, but there are three vent slits in its casing next to the MIO connector.
With the coolers removed, we can see that the two cards have similar component layouts:
Nvidia’s dual-PCB sandwiches are already a long-forgotten solution, the GeForce GTX 590 being designed in the same way as dual-processor Radeons. AMD and Nvidia put both GPUs on a single PCB but at somewhat different locations which are determined by the placement of the graphics memory chips which are themselves installed on each side of the PCB. There are eight memory chips for each GPU. As you can see, each PCB is highly sophisticated and populated with lots of components.
The Radeon HD 6990 carries two full-featured Cayman GPUs. I want to stress the fact that they are indeed full-featured because dual-processor cards used to be equipped with cut-down versions of GPUs in the past. The GPU frequency of the Radeon HD 6990 is only 50 MHz lower than that of the Radeon HD 6970 and equals 830 MHz. However, there is a high-speed mode you can trigger by means of the abovementioned switch near the CrossFireX connector. The card's GPU frequency is 880 MHz in that mode, but AMD says that turning that switch on will make your warranty void. The card’s GPU frequency is lowered to 150 MHz in 2D applications to save power.
Each of its GPUs has 1536 unified shader processors, 96 texture-mapping units and 32 raster back-ends. As is typical of AMD cards, there are no protective caps (heat-spreaders) on the GPUs:
As opposed to AMD, Nvidia equips its GPUs with such caps. The company didn’t disable any subunits in the GPUs of its GeForce GTX 590, either. Each of the card's GPUs has 512 unified shader processors, 64 texture-mapping units and 48 raster operators. In other words, we've got two GeForce GTX 580 processors on a single PCB here. Their frequencies are lowered more than those of the AMD Radeon HD 6990, though. The GeForce GTX 590 clocks its GPUs at 607/1215 MHz, which is 21.4% lower than the clock rates of the GeForce GTX 580 (772/1544 MHz). The reason for this reduction is clear enough. If Nvidia used the clock rates of the GTX 580 for the GTX 590, the latter's heat dissipation and power consumption would be beyond all reasonable limits. The GeForce GTX 590 drops its GPU clock rates to 51/101 MHz in 2D mode as a power-saving measure.
Both cards have GDDR5 memory in 16 BGA-packaged chips. The Radeon HD 6990 carries a total of 4 gigabytes of graphics memory (2 gigabytes per each GPU) whereas the GeForce GTX 590 has 1.5 gigabytes of onboard memory for each GPU or 3 gigabytes in total. As usual, AMD installs Hynix H5GQ2H24MFR T2C chips on its Cayman-based reference cards. These chips have a voltage of 1.5 volts and a rated frequency of 5000 MHz. The card's memory frequency is 5000 MHz, too, but is lowered to 600 MHz in 2D mode. The memory bus is 256 bits wide.
The GeForce GTX 590 comes with Samsung K4G10325FE-HC04 chips that have a rated access time of 0.4 nanoseconds and a rated frequency of 5000 MHz. However, the card clocks them at 3414 MHz only, which is 15% lower than the memory frequency of the GeForce GTX 580 and 10% lower than that of the GTX 570. The memory frequency is lowered to 270 MHz in 2D mode. The memory bus is 384 bits wide.
This is what the GPU-Z tool reports about the two cards:
Unfortunately, version 0.5.1 does not recognize the GeForce GTX 590 and I had already given the card back by the time version 0.5.2 was released (March 21).