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TekSpek GPU - Graphics
ATI Radeon 5800 series

ATI Radeon 5800 series

Date issued:


All personal computers (PCs) use some form of graphics to output the display on to a monitor or screen. Looking back over the last 15 years, there has seen significant development in what are termed 3D accelerators - dedicated graphics boards designed to render life-like images in real-time - and the market has been dominated by two companies: NVIDIA and ATI.

ATI, part of processor company AMD since 2006, released its latest graphics processing units (GPUs) in September 2009. Known as the Radeon HD 5800-series, this TekSpek explains what they are, which new features they bring to the table, and how they compete against NVIDIA's price-comparable GPUs.

Radeon HD 5800

Following on the back of the Radeon HD 4800-series, launched in June 2008, ATI has increased performance in practically every parameter by using a collection of cutting-edge technologies.

Bracketed in terms of price, ATI currently has two cards in the Radeon HD 5800 stable: the Radeon HD 5870 1,024MB ($399) and Radeon HD 5850 1,024MB. The two cards share the same basic architecture but the Radeon HD 5850's processing and, consequently, performance is pared-down to hit the lower price point.

Radeon HD 5870 and HD 5850 cards, currently available at most etailers, are being marketed by a large number of add-in board (AIB) partners.

Wider and faster - how?

Graphics workloads are inherently parallelisable, which means that programs can be broken down into instructions and run concurrently across a number of execution units. In an oversimplified sense, then, the greater the number of units, the faster the overall processing.

The Radeon HD 5800-series adds in greater processing power by packing in more of practically everything when compared to the previous-generation HD 4800-series, as shown by the table, below.

  ATI Radeon™ HD 4870 ATI Radeon™ HD 5850 ATI Radeon™ HD 5870
Process 55nm 40nm 40nm
Transistors 956M 2.15B 2.15B
Engine Clock 750 MHz 725 MHz 850 MHz
Stream Processors 800 1440 1600
Compute Performance 1.2 TFLOPs 2.09 TFLOPs 2.72 TFLOPs
Texture Units 40 72 80
Texture Filtrate 30.0 GTexels/s 52.2 GTexels/s 68.0 GTexels/s
ROPs 16 32 32
Pixel Filtrate 12.0 GPixels/s 23.2 GPixels/s 27.2 GPixels/s
Z/Stencil 48.0 GSamples/s 92.8 GSamples/s 108.8 GSamples/s
Memory Type GDDR5 GDDR5 GDDR5
Memory Clock 900 MHz 1000 MHz 1200 MHz
Memory Data Rate 3.6 Gbps 4.0 Gbps 4.8 Gbps
Memory Bandwidth 115.2 GB/s 128.0 GB/s 153.6 GB/s
Maximum Board Power 160W 170W 188W
Idle Board Power 90W 27W 27W

Adding in a larger number of processing units - called Stream Processors by ATI - means that both the Radeon 5-series cards have greater compute power when directly compared against the Radeon HD 4870, to the tune of 2.3x for the range-topping HD 5870.

Theoretical compute power is only one part of the GPU story, however. A GPU's memory-bandwidth is important because it enables the processing of effects once they've been 'computed', and having more bandwidth ensures that the GPU doesn't stall when the image-quality and resolution - usually selected in-game - are dialled-up.

What's the cost of extra performance?

In order to deliver extra performance from a wider, faster design, ATI has increased the transistor-count - the building blocks of computing silicon - by a factor of 2.2x, to 2.15bn.

Increasing sheer processing power this way means that heat becomes a real concern. ATI has used the latest 40nm process, manufactured by a fabrication company called TSMC, for the Radeon HD 5800-cards. Transistors based on 40nm are significantly smaller and more power-efficient than on 55nm. By adding more heat-generating transistors but reducing the per-transistor power-draw, ATI has managed to keep overall under-load board power below 200W.

Tellingly, idle power-draw has dropped dramatically, helped by better power regulation and improvements in chip fabrication.

Not just about hardware - DX11, OpenCL, DirectCompute, GPGPU

Rendering images is more than just about harnessing increased processing power. Modern graphics cards need to meet industry-wide standards such that developers can author code that will run on cross-company hardware.

Graphics-wise, the most common standards are DirectX and OpenGL. Known as APIs (Application Programming Interface), newer iterations provide a cleaner and tighter feature-set that enables better-looking effects with increased rendering speed.

Most games are based around Microsoft's DirectX. The latest iteration, DX11, will ship with the Windows 7 operating system on October 22, 2009, although users of Microsoft Vista will be able to download the update from DX10 to DX11 via Microsoft's servers a short while later.

DX11 main benefits are that it brings support for what's termed hardware tessellation - the ability for a GPU to create high-detail models from basic geometry, increasing efficiency - better multi-threading support for many-core CPUs that ship in the majority of systems today, and simpler access for GPGPU (General Processing on a Graphics Processing Unit) calculations.

The highly parallel, high-throughput design of modern GPUs enables them to perform certain non-gaming tasks at speeds far in excess of any CPU. Parallelisable workloads such as video-encoding and, in the professional space, complex calculations pertaining to oil and gas exploration/academia/medical world run especially well on a GPU, assuming that the application is well-coded. To this end, the Radeon HD 5800-series supports features such as high-speed double-precision computation, as well as newer standards such as OpenCL and DirectCompute, too.

Display choices

Another improvement of the new GPUs is support for a greater number of digital displays. Marketed by ATI under technology known as Eyefinity, both 5-series GPUs are internally plumbed to run up to six independent displays, although the majority of cards will feature three outputs, most likely DVI, HDMI, and DisplayPort.

The competition

Arch-rival NVIDIA has yet to launch a new range of cards, and industry watchers reckon that ATI has, at the very least, a three-month window of opportunity with the HD 5800-series.

However, at a GPU computing conference held in San Jose, California in late-September 2009, NVIDIA provided basic details for its competing products. Codenamed Fermi, it is practically impossible to determine whether retail models will be better GPUs than ATI's 5-series.

NVIDIA, it seems, will be deliberately architecting its GPUs to perform better in a GPGPU environment, backed up by the company's efforts in pushing an NVIDIA-only GPU-programming language known as CUDA, which helps developers and academics translate and port their computational problems on to the hardware via commonly-used C+.


The introduction of the Radeon 5870 and Radeon HD 5850 GPUs means that ATI has the fastest single-GPU graphics cards available. Greater processing is made possible by a more-efficient manufacturing process. Adherence to Microsoft's DX11 enables the GPUs to take advantage of newer gaming titles that use the API for better-looking effects which should, in some cases, render with increased speed.

ATI has a significant opportunity to leverage the architecture and derivate such that the bulk of its GPU catalogue, from top to bottom, is composed of 5-series parts before NVIDIA is able to launch its own parts, currently codenamed Fermi.