GT200b, GeForce GTX 200 series

GT200b specifications

• Code name: GT200b
• Process technology: 55nm
• 1.4 billion transistors
• Unified architecture with an array of common processors for streaming processing of vertices and pixels, as well as other data
• Hardware support for DirectX 10, including Shader Model 4.0, geometry generation, and stream output
• 512-bit memory bus, eight independent 64-bit controllers
• Core clock: 648 MHz
• More than doubled ALU frequency: 1476 MHz
• 240 scalar floating-point ALUs (integer and floating-point formats, support for FP32 and FP64 according to IEEE 754(R), two MAD+MUL per cycle)
• 80 texture address and filtering units, support for FP16 and FP32 components in textures
• Dynamic branching in pixel and vertex shaders
• 8 wide ROPs (32 pixels) supporting antialiasing with up to 16 samples per pixel, including FP16 or FP32 frame buffer. Each unit consists of an array of flexibly configurable ALUs and is responsible for Z generation and comparison, MSAA, blending. Peak performance of this subsystem is up to 128 MSAA samples (+ 128 Z) per cycle, in Z only mode - 256 samples per cycle
• Multiple render targets (up to 8 buffers)
• Interfaces (2 x RAMDAC, 2 x Dual DVI, HDMI, DisplayPort, HDTV) are integrated into a separate chip.

GeForce GTX 285 specifications

• Core clock: 648 MHz
• Unified processors frequency: 1476 MHz
• Unified processors: 240
• 80 texture units, 32 blending units
• Effective memory frequency: 2484 (2*1242) MHz
• Memory type: GDDR3
• Memory: 1024 MB
• Memory bandwidth: 159 GB/s
• Maximum theoretical fillrate: 20.7 gigapixel per second
• Theoretical texture sampling rate: 51.8 gigatexel per second
• 2 x DVI-I Dual Link, 2560x1600 video output
• Double SLI connector
• PCI Express 2.0
• TV-Out, HDTV-Out, HDCP support, HDMI, DisplayPort
• Power consumption: up to 183W (two 6-pin connectors)
• Dual-slot design
• MSRP: $349

As GT200b chips are manufactured by the 55nm process technology, NVIDIA can actually launch an overhauled solution with a new name and improved performance, instead of simply replacing the GPU in GeForce GTX 280. Along with improved performance, this solution consumes much less power than its predecessor (GTX 280).

The overhauled card from NVIDIA offers similar performance at a lower power consumption level. Even though GT200b GPUs are manufactured by the 55nm process technology just like RV770 chips, they have much larger surface area and complexity (the number of transistors), but these solutions consume less power than their competitors.

From the user's point of view, nothing has changed in GTX 285 compared to GTX 280, except for the GPU, a new PCB design, and slightly better characteristics. But along with a minor increase in operating frequencies, GTX 285 features significantly reduced power consumption. GeForce GTX 280, based on the 65nm GT200 GPU, consumes up to 236W. Having upgraded GT200 to the 55nm process technology, the company reduced maximum power consumption to 183W, almost by one third!

As a result, we've got not only reduced requirements to power supply, but also changes in extra power connectors. Relatively low power consumption allows to install two 6-pin connectors instead of 8-pin and 6-pin ones. They are prevalent, especially in power supply units.

GeForce GTX 275 specifications

• Core clock: 633 MHz
• Unified processors frequency: 1404 MHz
• Unified processors: 240
• 80 texture units, 28 blending units
• Effective memory frequency: 2268 MHz (2*1134)
• Memory type: GDDR3
• Memory: 896 MB
• Memory bandwidth: 127 GB/s
• Maximum theoretical fillrate: 17.7 gigapixel per second
• Theoretical texture sampling rate: 50.6 gigatexel per second
• 2 x DVI-I Dual Link, 2560x1600 video output
• Double SLI connector
• PCI Express 2.0
• TV-Out, HDTV-Out, HDCP support, HDMI, DisplayPort
• Power consumption: up to 219W (two 6-pin connectors)
• Dual-slot design
• MSRP: $259

We already mentioned that GT200b GPUs being manufactured by the 55nm process technology, NVIDIA managed to replace the old GeForce GTX 260 and GTX 280 with new faster products. But the company also rolled out a new GTX 275 card to compete with RADEON HD 4890. Along with improved performance, this solution consumes less power than its predecessors.

Take a look at memory volume and the name of this product. This amount of video memory is determined by the PCB from the overhauled GTX 260 card with a 448-bit memory bus. Thus we have 896MB here. It's sufficient for the great majority of applications.

The new card from NVIDIA is a tad faster than GTX 260, so it was logically called GTX 275. This change in its product number makes sense to users, it shows that the card stands in between GTX 260 and GTX 285. Figure five in the end stands for the 55nm GPU, and thus improved characteristics (power consumption and heat release).

GeForce GTX 295 specifications

• Core clock: 576 MHz
• Unified processors frequency: 1242 MHz
• Unified processors: 480 (2 x 240)
• 160 (2 x 80) texture units, 56 (2 x 28) blending units
• Effective memory frequency: 2000 MHz (2*1000)
• Memory type: GDDR3
• Memory: 1792MB (896 x 2)
• Memory bandwidth: 2 x 112 GB/s
• Maximum theoretical fillrate: 2 x 16.1 gigapixel per second
• Theoretical texture sampling rate: 2 x 46.1 gigatexel per second
• 2 x DVI-I Dual Link, 2560x1600 video output
• Single SLI connector
• PCI Express 2.0
• TV-Out, HDTV-Out, HDCP support, HDMI, DisplayPort
• Power consumption: up to 289W (8-pin and 6-pin connectors)
• Dual-slot design
• MSRP: $499

The 55nm process technology used to manufacture GT200b chips allows NVIDIA to design a powerful dual-GPU solution. The new card from NVIDIA offers higher performance at the power consumption level of HD 4870 X2. It's all the more unexpected, as GT200b GPUs have much larger surface area and complexity (the number of transistors) than RV770 chips, which are also manufactured by the 55nm process technology.

NVIDIA decided to launch a dual-GPU card with the same GTX suffix, only the model number if different. That was the decision, but it would have been more logical to give this card a different name, like GX2 290 or G2X 290. Even SLI 290 would be easier to understand for common users. And this product name does not indicate that the card has two GPUs. It may confuse customers.

To all appearances, this 448-bit bus and 896MB per each GPU may have to do with a decision to simplify PCB layout. As a result, we get unusual memory volume. And more importantly, it's lower than in RADEON HD 4870 X2. Although the difference between 896MB and 1024MB is not big, and it does not affect performance that much, it's not good from the marketing point of view. Even though nominally, this product is 'worse' than its competitor, judging by one of its specification parameters (and marketing people just love these things!)

Dual-GPU peculiarities

GT200b GPUs do not differ from GT200 ones, except for smaller surface and higher power efficiency. GT200 architecture was announced last summer. And if we take into account that it's actually the improved G8x/G9x architecture, it appeared even earlier -- in 2006. The main difference between G92 and G80 was the 65nm process technology, GT200 featured mostly quantitative changes, and GT200b is no different from GT200. You can read about it above.

NVIDIA decided to equip the GTX 295 with sterling GT200 GPUs (240 ALUs and 80 texture units each). However, they preserved memory configuration from GTX 260 -- 448-bit bus and 896MB of GDDR3 memory per GPU. Just like the GTX 260, each GPU in the GTX 295 uses only seven wide ROPs out of eight available in the chip, which gives us 56 ROPs.

Clock rates of the GPU match those of the single GeForce GTX 260 completely. Frequency of the GPU, TMUs and ROPs equals 576 MHz, and stream processors operate at 1242 MHz. GDDR3 memory works at 1000(2000) MHz.

As in all previous dual-GPU solutions, a special chip is installed between the GPUs to connect them. In this case we have nForce 200 (BR-04) that supports a necessary number of lanes for three PCI-E 2.0 ports. Sixteen PCI-E 2.0 lanes are assigned to each GPU, and as many lanes are used to exchange data between a motherboard and this graphics card.

This PCI-E bridge was installed on the previous dual-GPU solution from this company. Besides, nForce 200 was also offered as an alternative SLI solution for motherboards with the Intel X58 chipset.

Like a previous NVIDIA's dual-GPU solution (GeForce 9800 GX2), the new GeForce GTX 295 uses two PCBs. That is each GPU is mounted on its own PCB. This design has some advantages: each GPU heats only one PCB; the cooler chills both GPUs simultaneously, unlike GeForce 7950 GX2, which uses two cooling systems. However, NVIDIA will soon redesign GTX 295 as a single-PCB solution.

Maximum power consumption of GeForce GTX 295 amounts to 289W, which is similar to that of RADEON HD 4870 X2 (286W). The card requires two power connectors: 6-pin and 8-pin ones. And a power supply unit for a single GeForce GTX 295 should be at least 680W.

Write a comment below. No registration needed!