Nvidia GeForce GTX 200: PCB Design and Functionality

As we have already mentioned several times, Nvidia is attracted to all gigantic. While using a long PCB and a strong power supply system wasn’t absolutely necessary for Nvidia GeForce 9800 GTX, the new graphics cards family on Nvidia G200 tells a completely different story.

Even at first glance both new cards look just the opposite from ATI Radeon HD 4800 illustrating the different approaches to GPU and graphics cards design chosen by two main players of the graphics market. Huge PCB and extremely complex layout are an inevitable necessity resulting from high power consumption of the graphics core. They used not the most advance manufacturing process for the core consisting of 1.4 billion transistors, which is an absolute record. The 512bit memory bus also contributed to the layout complexity, while ATI’s new solutions still use a simpler 256-bit bus. Both cards, GTX 280 and GTX 260, use unified design that makes it rally hard to joggle the prices. Also, graphics cards with proprietary layouts are also very unlikely to appear, because of extremely complex Nvidia GeForce GTX 200 PCB design.

Nvidia GeForce GTX 280/260 hidden inside the cooling system are not very interesting from the technical prospective, because all the details are right beneath the solid massive casing, which is very hard to remove. The front and he back of the casing are held together with crews and special clips, which we have already seen before. For example, the casing of Nvidia GeForce 8800 GT cooler used the same clips.

It is pretty hard to take the casing apart, but we did it nevertheless, and revealed all the most exciting parts of the card.

The voltage regulator circuitry takes up the entire right part of the PCB, about 1/3. As we have expected, it turned out pretty powerful. There is a seven-phase regulator circuitry with a Volterra VT1165MF PWM controller that is responsible for supplying GPU with power. Voltage regulators like that, using almost no traditional electrolytic capacitors, are often referred to as digital. However, it is actually completely wrong: the only difference from traditional regulators is in the higher operational frequency, which allows trading electrolytic capacitors for smaller ceramic ones. It makes the entire system much more reliable. Moreover, it would be very hard to fit a lot of electrolytic capacitors even on a large PCB like that, so the biggest advantages of the new high-frequency voltage regulator are its reliability and small size. Nvidia GeForce GTX 260 has 5 phases instead of 7 and fewer electronic components on the PCB.

The GPU consisting of 1.4 billion transistors and manufactured with 65nm process should boast horrific power consumption that is why it makes total sense to have two additional power supply connectors. Nvidia GeForce GTX 280 has one 8-pin connector that can bear up to 150W. Note that you can’t connect a 6-pin power cable to it – the card will not power on and a red light on the bracket will indicate power problems. The “lighter” GeForce GTX 260 uses the same PCB, but with a pair of regular 6-pin PCI Express 1.0 connectors with 75W capacity. It has no LED indicator either.

Memory voltage regulator is based on Richtek RT9259A chip that we have already come across before in our Gainward and ECS solutions reviews. Since its components are located around the power part of the PCI Express x16 slot, we can conclude that memory received its power from this PCB segment. So, all additional power connectors service GPU only, which is not surprising at all considering its serious appetite for power.

Nvidia used a completely different approach to increasing the memory bandwidth than ATI that bet on increasing the frequency due to faster GDDR5 memory. Nvidia GeForce GTX 200 family had its memory bandwidth increased in a more traditional way: by using a wider 512bit bus for the top model and 448bit bus for the slower model. The latter uses two memory chips less, which determines the corresponding capacity and width. They doubled the number of spots for the memory chips: new cards can accommodate up to 16 chips instead of 8, with half the spots located on the reverse side of the PCB.

Nvidia GeForce GTX 280 memory

Nvidia GeForce GTX 260 memory 

Wider memory bus makes the PCB layout much more complex and expensive to produce, however, it is partially compensated by more widely spread and cheaper memory GDDR3 chips. Both graphics cards discussed today use the same Hynix H5RS5223CFR 512Mbit (16Mx32) chips. Nvidia GeForce GTX 280, however, uses chips modification with N2C suffix that operates at 1200 (2400) MHz, while Nvidia GeForce GTX 260 is equipped with slower N0C chips working at 1000 (2000) MHz nominal frequency. In the first case the memory is clocked at a slightly lower frequency of 1100 (2200) MHz, while in the second case the frequency equals the nominal 1000 (2000) MHz. The top model features 1024MB of memory, while the slower model is equipped with 896MHz.

Since Nvidia GeForce GTX 280 and Nvidia GeForce GTX 260 have different memory bus width, their memory subsystem bandwidths make 140.8GB/s and 112GB/s respectively. So, from this prospective, the top model is far ahead of ATI Radeon HD 4870, while the other one yields to it a little bit. However, as we have already pointed out several times with ATI R600 as an example, it is not enough to have significant memory subsystem bandwidth, you should be able to take advantage of it in a smart way. ATI Radeon HD 4870 proved capable of that, however only tests will show what we can expect from Nvidia GeForce GTX 200 here.

Nvidia GeForce GTX 280 GPU

Nvidia GeForce GTX 260 GPU

The size of the graphics processor is truly impressive: it is a real giant, just like G80 was. Unfortunately, we can’t really see because we couldn’t remove the chip heat-spreader easily and decided not to apply any force to it fearing to damage the die. However, the number mentioned earlier will give you a good idea of the size: 576sq.mm. It makes ATI RV770 and Nvidia G92 look like midgets with their 260 and 330sq.mm sizes. This is the price you have to pay for the record-breaking number of transistors and not the most advanced production process. Unlike Nvidia GeForce 8800 GTX, the new G200 based solutions have no metal frame around the GPU edges, although there is a spot for it.

Nvidia’s chip marking is more informative than ATI’s, because it also indicates clearly that the new chip is codenamed G200 and not GT200, D10U, NV55 or NV60. Both chips have A2 revision and are manufactured on week 18 2008, between April 27 and May 3. The interesting thing is that the chip on board of Nvidia GeForce GTX 280 is marked as G200-300-A2, while the chip on Nvidia GeForce GTX 260 – as G200-100-A2. Looks like the middle number has to do with frequency and/or number of operational functional units. With a die that huge G200 yields could be extremely low, so Nvidia may be using not only the chips with lower frequency potential, but also the ones with several defective units.

Nvidia GeForce GTX 280 has all core units up and running: 240 unified shader processors, 80 texturing processors and 32 raster units. Its operational frequency equals 602MHz for the main domain and 1296MHz for the computational one. Nvidia GeForce GTX 260 has more modest features: only 192 active shader processors, 64 texturing units and 28 RBE. Its core frequencies are 576/1242MHz respectively.

Just like by Nvidia G80 based graphics cards, the display controllers are singled out in a separate NVIO chip located to the left of the GPU next to the DVI connectors. This prevented the record-breaking number of transistors in the main die from getting even higher than that.

The marking reads NVIO2-A2, the second version of NVIO chip. However, its functionality remained the same and it still doesn’t support DisplayPort interface. There is a special spot for the translator chip on the card PCB right beneath the MIO connectors. There is also a contact slot laid out for the corresponding connector right above the top DVII port. However, we doubt they will ever roll out Nvidia GeForce GTX 200 with this interface onboard. As for MIO, both Nvidia GeForce GTX 200 models have two of these, so that you could use them in triple-SLI configurations. Their power consumption and heat dissipation will certainly be on the corresponding level, which will barely please even the most risky enthusiasts. SLI connectors are covered with protective rubber caps.

There is a plastic panel above the seven-pin mini-DIN connector functioning as an analogue video out, so you will be able to see the glowing of the LED indicating the power status of your Nvidia GeForce GTX 280 through the slits in the bracket. If everything is OK, it glows green; but if one of the connectors is not plugged in properly or if there is a 6-pin plus in the 8-pin connector socket, it will glow red and the card won’t start. As for the additional functions, we have to mention a two-pin connector next to the power supply connectors that you use to connect to a sound card to translate the sound from S/PDIF to HDMI, because G200 has no proprietary sound core. The only interesting thing about the reverse side of the PCB is the insulation pads beneath the DVI and mini-DIN ports. Since the card is locked within a solid metal casing of the cooling system, these pads prevent electric locking.