Radeon R520
Encyclopedia
ATI's "R520" core is the foundation for a line of DirectX
DirectX
Microsoft DirectX is a collection of application programming interfaces for handling tasks related to multimedia, especially game programming and video, on Microsoft platforms. Originally, the names of these APIs all began with Direct, such as Direct3D, DirectDraw, DirectMusic, DirectPlay,...

 9.0c and OpenGL
OpenGL
OpenGL is a standard specification defining a cross-language, cross-platform API for writing applications that produce 2D and 3D computer graphics. The interface consists of over 250 different function calls which can be used to draw complex three-dimensional scenes from simple primitives. OpenGL...

 2.0 3D accelerator X1000 video card
Video card
A video card, Graphics Card, or Graphics adapter is an expansion card which generates output images to a display. Most video cards offer various functions such as accelerated rendering of 3D scenes and 2D graphics, MPEG-2/MPEG-4 decoding, TV output, or the ability to connect multiple monitors...

s. It is ATI's first major architectural overhaul since the "R300
Radeon R300
The Radeon R300 is the third generation of Radeon graphics chips from ATI Technologies. The line features 3D acceleration based upon Direct3D 9.0 and OpenGL 2.0, a major improvement in features and performance compared to the preceding Radeon R200 design. R300 was the first fully Direct3D...

" core and is highly optimized for Shader Model 3.0. The Radeon
Radeon
Radeon is a brand of graphics processing units and random access memory produced by Advanced Micro Devices , first launched in 2000 by ATI Technologies, which was acquired by AMD in 2006. Radeon is the successor to the Rage line. There are four different groups, which can be differentiated by...

 X1000 series
using the core was introduced on October 5, 2005, and competed primarily against nVidia's GeForce 7000 series
GeForce 7 Series
The GeForce 7 Series is the seventh generation of Nvidia's GeForce graphics processing units.-Features:The following features are common to all models in the GeForce 7 series except the GeForce 7100, which lacks GCAA:-GeForce 7100 Series:...

. ATI released the successor to the R500 series with the R600
Radeon R600
The graphics processing unit codenamed the Radeon R600 is the foundation of the Radeon HD 2000/3000 series and the FireGL 2007 series video cards developed by ATI Technologies...

 series on May 14, 2007. ATI does not provide official support for any X1000 series cards for Windows 7.

Architecture

The R520 core architecture is referred to by ATI as an "Ultra Threaded
Thread (computer science)
In computer science, a thread of execution is the smallest unit of processing that can be scheduled by an operating system. The implementation of threads and processes differs from one operating system to another, but in most cases, a thread is contained inside a process...

 Dispatch Processor". This refers to ATI's plan to boost the efficiency of their core, instead of going with a brute force increase in the number of processing units. A central pixel shader "dispatch unit" breaks shaders down into threads (batches) of 16 pixels (4×4) and can track and distribute up to 128 threads per pixel "quad" (4 pipelines each). When one of the shader quads becomes idle, due to a completion of a task or waiting for other data, the dispatch engine will assign the quad with another task to do in the meantime, with the overall result being a greater utilization of the shader units, theoretically. With such a large number of threads per "quad", ATI created a very large general purpose register array that is capable of multiple concurrent reads and writes and has a high-bandwidth connection to each shader array. This provides temporary storage necessary to keep the pipelines fed by having work available as much as possible. With chips such as RV530 and R580, where the number of shader units per pipeline triples, the efficiency of pixel shading drops off slightly because these shaders still have the same level of threading resources as the less endowed RV515 and R520.

The next major change to the core is with its memory bus. R420
Radeon R420
The Radeon R420 core from ATI Technologies was the company's basis for its 3rd-generation DirectX 9.0/OpenGL 2.0-capable graphics cards. Used first on the Radeon X800, R420 was produced on a 0.13 micrometer low-K process and used GDDR-3 memory...

 and R300 had nearly identical memory controller designs, with the former being a bug fixed release designed for higher clock speeds. R520, however, differs with its central controller (arbiter) that connects to the "memory clients". Around the chip there are two 256-bit ring buses running at the same speed as the DRAM
Dram
Dram or DRAM may refer to:As a unit of measure:* Dram , an imperial unit of mass and volume* Armenian dram, a monetary unit* Dirham, a unit of currency in several Arab nationsOther uses:...

 chips, but in opposite directions to reduce latency. Along these ring buses are 4 "stop" points where data exits the ring and going into or out of the memory chips. There is actually a fifth stop, one that is significantly less complex, designed for the PCI Express
PCI Express
PCI Express , officially abbreviated as PCIe, is a computer expansion card standard designed to replace the older PCI, PCI-X, and AGP bus standards...

 interface and video input. This design allows memory accesses to be far quicker though lower latency by virtue of the smaller distance the signals need to move through the GPU, and by increasing the number of banks per DRAM. Basically the chip can spread out memory requests faster and more directly to the RAM chips. ATI claims a 40% improvement in efficiency over older designs. Again, the smaller cores such as RV515 and RV530 receive cutbacks due to their smaller, less costly designs. RV530, for example, has two internal 128-bit buses instead. This generation has support for all recent memory types, including GDDR4
GDDR4
GDDR4 SDRAM is a type of graphics card memory specified by the JEDEC Semiconductor Memory Standard. It is a rival medium to Rambus's XDR DRAM...

. In addition to ring bus, each memory channel now has the granularity of 32-bits, which improves memory efficiency when performing small memory requests.

The vertex shader engines were already of the required FP32
Floating point
In computing, floating point describes a method of representing real numbers in a way that can support a wide range of values. Numbers are, in general, represented approximately to a fixed number of significant digits and scaled using an exponent. The base for the scaling is normally 2, 10 or 16...

 precision in ATI's older products. Changes necessary for SM3.0 included longer instruction lengths, dynamic flow control instructions, with branches, loops and subroutines and a larger temporary register space. The pixel shader engines are actually quite similar in computational layout to their R420 counterparts, although they were heavily optimized and tweaked to reach high clock speeds on the 90 nm process. ATI has been working for years on a high-performance shader compiler in their driver for their older hardware, so staying with a similar basic design that is compatible offered obvious cost and time savings.

At the end of the pipeline, the texture addressing processors are now decoupled from pixel shader, so any unused texturing units can be dynamically allocated to pixels that need more texture layers. Other improvements include 4096x4096 texture support and ATI's 3Dc normal map compression sees an improvement in compression ratio for more specific situations.

The R5xx family introduced a more advanced onboard motion-video engine. Like the Radeon cards since the R100, the R5xx can offload almost the entire MPEG-1/2 video pipeline. The R5xx can also assist in Microsoft WMV9/VC-1
VC-1
VC-1 is the informal name of the SMPTE 421M video codec standard, which was initially developed as a proprietary video format by Microsoft before it was released as a formal SMPTE standard video format on April 3, 2006...

 and MPEG H.264/AVC decoding, by a combination of the 3D/pipeline's shader-units and the motion-video engine. Benchmarks show only a modest decrease in CPU-utilization for VC-1 and H.264 playback.

As is typical for an ATI video card release, a selection of real-time 3D demonstration programs were released at launch. ATI's development of their "digital superstar", Ruby, continued with a new demo named The Assassin. The demo showcased a highly complex environment, with high dynamic range lighting
High dynamic range rendering
In 3D computer graphics, high dynamic range rendering , also known as high dynamic range lighting, is the rendering of computer graphics scenes by using lighting calculations done in a larger dynamic range. This allows preservation of details that may be lost due to limiting contrast ratios...

 (HDR) and dynamic soft shadows. Ruby's latest nemesis, Cyn, was composed of 120,000 polygons.

The cards support dual-link DVI
Digital Visual Interface
The Digital Visual Interface is a video interface standard covering the transmission of video between a source device and a display device. The DVI standard has achieved widespread acceptance in the PC industry, both in desktop PCs and monitors...

 output and HDCP
High-Bandwidth Digital Content Protection
High-bandwidth Digital Content Protection is a form of digital copy protection developed by Intel Corporation to prevent copying of digital audio and video content as it travels across connections...

. However, using HDCP requires external ROM to be installed, which were not available for early models of the video cards. RV515, RV530, RV535 cores include 1 single and 1 double DVI link; R520, RV560, RV570, R580, R580+ cores include 2 double DVI links.

AMD has released the final Radeon R5xx Acceleration document.

X1300–X1550 series

This series is the budget solution of the X1000 series and is based on the RV515 core. The chips have 4 texture units
Texture mapping unit
A texture mapping unit is a component in modern graphics processing units , historically it is a separate physical processor. A TMU is able to rotate and resize a bitmap to be placed onto an arbitrary plane of a given 3D object as a texture...

, 4 ROPs
Render Output unit
The Render Output Unit, often abbreviated as "ROP", and sometimes called Raster Operations Pipeline, is one of the final steps in the rendering process of modern 3D accelerator boards. The pixel pipelines take pixel and texel information and process it, via specific matrix and vector operations,...

, 4 pixel shaders, and 2 vertex shaders, similar to the older X300 - X600
Radeon R300
The Radeon R300 is the third generation of Radeon graphics chips from ATI Technologies. The line features 3D acceleration based upon Direct3D 9.0 and OpenGL 2.0, a major improvement in features and performance compared to the preceding Radeon R200 design. R300 was the first fully Direct3D...

 cards. These chips basically use 1 "quad" (referring to 4 pipelines) of a R520, whereas the faster boards use just more of these "quads". For example, the X1800 uses 4 "quads". This modular design allows ATI to build a "top to bottom" line-up using identical technology, saving research and development time and money. Because of its smaller design, these cards also offer lower power demands (30 watts), so they run cooler and can be used in smaller cases.
Eventually, ATI created the X1550, little more than an X1300 in disguise, and discontinued the X1300. The X1050 was based on the R300 core and was sold as an ultra-low-budget part.

Early Mobility Radeon X1300 to X1450 are based around the RV515 core as well.

Beginning in 2006, Radeon X1300 and X1550 products were shifted to the RV505 core, which had similar capabilities and features as the previous RV515 core, but was manufactured by TSMC using an 80nm process (reduced from the 90nm process of the RV515).

X1600 series

X1600 uses the M56 core which is based on RV530 core, a core similar but distinct from RV515.

The RV530 has a 3:1 ratio of pixel shaders to texture units. It possesses 12 pixel shaders while retaining RV515's 4 texture units and 4 ROPs. It also gains three extra vertex shaders, bringing the total to 5 units. The chip's single "quad" has 3 pixel shader processors per pipeline, similar to the design of R580's 4 quads. This means that RV530 has the same texturing ability as the X1300 at the same clock speed, but with its 12 pixel shaders it encroaches on X1800's territory in shader computational performance. Unfortunately, due to the programming content of available games, the X1600 is greatly hampered by lack of texturing power.

The X1600 was positioned to replace Radeon X600 and Radeon X700 as ATI's mid-range GPU. The Mobility Radeon X1600 and X1700 are also based on RV530.

X1650 series

The X1650 series has two parts, which are quite different with regards to performance. The X1650 Pro uses the RV535 core (which is a RV530 core manufactured on the newer 80 nm process). Its advantage over X1600 is both lower power consumption and heat output.

The other part, the X1650XT, uses the newer RV570 core (also known as the RV560) although cut down in processing power (note that the fully equipped RV570 core powers the X1950Pro, a high-performance card) to match its main competitor, NVIDIA's 7600GT.

X1800 series

Originally the flagship of the X1000 series, the X1800 series was released with little fanfare due to the rolling release
Rolling release
In software development, a rolling release development model refers to a continuously developing software system; this is opposed to a standard release development model which uses software versions that must be reinstalled over the previous version...

 and the gain by its competitor at that time, NVIDIA’s GeForce 7 Series
GeForce 7 Series
The GeForce 7 Series is the seventh generation of Nvidia's GeForce graphics processing units.-Features:The following features are common to all models in the GeForce 7 series except the GeForce 7100, which lacks GCAA:-GeForce 7100 Series:...

. The reason for the delayed release was that ATI engineers had found a bug within the core caused by a faulty 3rd party 90 nm chip design library which greatly hampered clock speed ramping, and so they had to "respin" it for another revision. The problem had been almost random in how it affected the prototype chips, making it quite difficult to finally identify. When the R520 hit the market in late 2005, the X1800 was the first high-end 90 nm GPU. ATI opted to fit the cards with either 256 MiB
MIB
MIB may refer to any of several concepts:* Master of International Business, a postgraduate business degree* Melayu Islam Beraja, the adopted national philosophy of Brunei* Motion induced blindness, a visual illusion in peripheral vision...

 or 512 MiB on-board memory (foreseeing a future of ever growing demands on local memory size). The X1800XT PE was exclusively on 512 MiB on-board memory. The X1800 replaced the R480-based Radeon X850 as ATI's premier performance GPU.

With R520's delayed release, its competition was far more impressive than it would have been if the chip had made its originally scheduled Spring/Summer '05 release. Like its predecessor X850, the R520 chip carries 4 "quads" (4 pipelines each), which means it has similar texturing capability if at the same clock speed as its ancestor, and the NVIDIA 6800 series. Contrasting the X850 however, R520's shader units are vastly improved. Not only are they fully Shader Model 3 capable, but ATI introduced some innovative advancements in shader threading that can greatly improve the efficiency of the shader units. Unlike the X1900, the X1800 has 16 pixel shader processors as well, and equal ratio of texturing to pixel shading capability. The chip also ups the vertex shader number from 6 on X800 to 8. And, with the use of the 90 nm Low-K
Low-K
In semiconductor manufacturing, a low-κ dielectric is a material with a small dielectric constant relative to silicon dioxide. Although the proper symbol for the dielectric constant is the Greek letter κ , in conversation such materials are referred to as being "low-k" rather than "low-κ"...

 fabrication process, these high-transistor chips could still be clocked at very high frequencies. This is what gives the X1800 series the ability to be competitive with GPUs with more pipelines but lower clock speeds, such as the NVIDIA 7800 and 7900 series that use 24 pipelines.

X1800 was quickly replaced by X1900 because of its delayed release. X1900 was not behind schedule, and was always planned as the "spring refresh" chip. However, due to the large quantity of unused X1800 chips, ATI decided to kill 1 quad of pixel pipelines and sell them off as the X1800GTO.

X1900 and X1950 series

The X1900 and X1950 series fixes several flaws in the X1800 design and adds a significant pixel shading performance boost. The R580 core is pin compatible with the R520 PCBs
Printed circuit board
A printed circuit board, or PCB, is used to mechanically support and electrically connect electronic components using conductive pathways, tracks or signal traces etched from copper sheets laminated onto a non-conductive substrate. It is also referred to as printed wiring board or etched wiring...

 meaning that a redesign of the X1800 PCB was not needed. The boards carry either 256 MB or 512 MiB of onboard GDDR3
GDDR3
Graphics Double Data Rate 3 is a graphics card-specific memory technology, designed by ATI Technologies with the collaboration of JEDEC.It has much the same technological base as DDR2, but the power and heat dispersal requirements have been reduced somewhat, allowing for higher performance memory...

 memory depending on the variant. The primary change between R580 and R520 is that ATI changed the pixel shader processor to texture processor ratio. The X1900 cards have 3 pixel shaders on each pipeline instead of 1, giving a total of 48 pixel shader units. ATI has taken this step with the expectation that future 3D software will be more pixel shader intensive.

In the latter half of 2006, ATI introduced the Radeon X1950 XTX. This is a graphics board using a revised R580 GPU called R580+. R580+ is the same as R580 except for support of GDDR4
GDDR4
GDDR4 SDRAM is a type of graphics card memory specified by the JEDEC Semiconductor Memory Standard. It is a rival medium to Rambus's XDR DRAM...

 memory, a new graphics DRAM
Dynamic random access memory
Dynamic random-access memory is a type of random-access memory that stores each bit of data in a separate capacitor within an integrated circuit. The capacitor can be either charged or discharged; these two states are taken to represent the two values of a bit, conventionally called 0 and 1...

technology that offers lower power consumption per clock and offers a significantly higher clock rate ceiling. X1950 XTX clocks its RAM at 1 GHz (2 GHz DDR), providing 64.0 GB/s of memory bandwidth, a 29% advantage over the X1900 XTX. The card was launched on August 23, 2006.

The X1950 Pro was released on October 17, 2006 and was intended to replace the X1900GT in the competitive sub-$200 market segment. The X1950 Pro GPU is built from the ground up on the 80 nm RV570 core with only 12 texture units and 36 pixel shaders. The X1950 Pro is the first ATI card that supports native Crossfire implementation by a pair of internal Crossfire connectors, which eliminates the need for the unwieldy external dongle found in older Crossfire systems.

External links

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