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The Accelerated Graphics Port (AGP) is a dedicated interface on the PC platform that enables high-performance graphics and full-motion video on mainstream PCs. The AGP interface, positioned between the PC's chip set and graphics controller, significantly increases the bandwidth available to a graphics accelerator (current peak bandwidth of 528 MB/s). It also helps to alleviate the cost pressure associated with a growing need for large and expensive dedicated graphics memories by leveraging a PC's main memory, in addition to local graphics memory.
By leveraging main memory, Independent Software Vendors (ISVs) are no longer constrained by the amount of dedicated local graphics memory in limiting the visual quality of their applications. Using main memory as if it were an extension of the dedicated local graphics memory, ISVs have significantly more storage space available for graphics data, which permits a significant increase in visual quality. Not only does AGP improve 3D graphics, but its increased bandwidth is a key enabler for full-motion video on the PC, such as host-based software MPEG-2 playback (DVD).
AGP lays a scalable foundation for high-performance graphics—future systems will support an AGP peak bandwidth over 1GB/s. An AGP enabled system requires an AGP-compatible: graphics accelerator chip or add-in card, chip set, BIOS, and motherboard. The AGP specification, which has been led by Intel and made available to the industry, is a key building block for Intel's Visual Computing Initiative.
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Merely delivering an AGP compatible product in a PC is not good enough to meet the demands of today's savvy PC purchasers. Enabling high-performance graphics for developers, as well as for PC users, requires significant planning to eliminate "weak links" in other parts of a PC system. With the Pentium® II processor and its Dual Independent Bus (DIB) architecture, Intel has proactively taken steps to "raise the bar" in terms of performance for other parts of the PC system. First, the extremely powerful floating-point performance of the Pentium II processor is the foundation for high-performance graphics. This permits ISVs to develop a new class of applications that can deliver life-like experiences to PC users. Second, the Pentium II processor's integrated L2 cache within the Single Edge Contact Cartridge permits the L2 cache frequency and performance to scale with the higher frequency CPUs that Intel will be delivering throughout 1998. A significant weakness of a Socket-7 AGP implementation is that the L2 cache performance does not scale with the CPU. Third, the DIB architecture allows the Pentium II processor to be performing 3D calculations while at the same time an AGP graphics accelerator can be performing AGP Texturing (i.e., directly executing textures from main memory). Doing this work in parallel is in part delivered by Intel®'s 440LX AGPset, which can be found in today's Pentium II processor based systems at mainstream price points. Again, the lack of this concurrency is another weakness of a Socket-7 AGP implementation.
Some of the first applications optimized for AGP are beginning to show up on store shelves. For example, Psygnosis' G-Police, a flight simulation title that is set in a Bladerunner-like future, is now available. The AGP-enabled version of G-Police provides richer backgrounds, more spectacular special effects, and even uses full-motion video textures on city billboards within the application.
In addition to arcade-quality 3D games, consumers can expect entirely new classes of applications to be enabled by AGP, such as 3D reference works and interactive video titles. Business users will also see new types of applications resulting from AGP, such as 3D visualization and interactive 3D web applications.
Here is just a sample of some applications that are being optimized to take advantage of the benefits of AGP. Some of these applications have already started showing up on store shelves, and others will arrive in early 1998 and throughout the year. (A few of these applications are still in early development):
Application |
Developer |
Publisher |
Category |
G-Police |
Psygnosis |
Psygnosis |
Flight simulation |
Red Line Racer |
Criterion Studios |
Ubi Soft Entertainment |
Motorcycle racing |
Tonic Trouble |
Ubi Soft Entertainment |
Ubi Soft Entertainment |
Kids action/adventure |
Eyewitness Virtual |
DK Multimedia |
DK Multimedia |
Education/refer. - DVD |
O-Zone |
Pixel |
Electronic Arts |
Online action game |
F22: Air Dominance |
Digital Image Design |
Ocean-Infogames |
Flight simulation |
Beyond the 3rd Dimen. |
Davidson and Assoc. |
CUC |
Kids education/game |
Tex Murphy: Overseer |
Access Software |
Access Software |
Detective game - DVD |
ConceptCAD |
Virtus Corporation |
Virtus Corporation |
3D Visualization |
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One of the benefits of Intel re-doubling its efforts to deliver processors to meet the needs of PC OEMs and the marketplace in general, is that AGP will find its way into systems priced very aggressively in the second half of '98. In fact, it is anticipated that a system with AGP will be part of the Basic Desktop PC in the second half of '98. This eliminates the short-term cost benefits others thought might exist for a Socket-7 AGP implementation. Also note that Intel has designed and delivered a software patch (AGP VxD) to support all of the AGP benefits on Windows* 95—you can deliver all of the AGP benefits for your customers today. Finally, taking graphics off of PCI and putting it on AGP does not address the other weaknesses of a Socket-7 AGP implementation; that is, it still does not address the L2 cache inefficiencies or the bottleneck in getting to main memory. In fact, if one starts storing texture maps in main memory (which is one of the cost savings benefits of AGP) on a Socket-7 AGP implementation, it may make the main memory bottleneck even worse.
AGP takes PCs to a new level of performance. Exciting arcade-quality games and new classes of applications promise to grow the overall market for PCs, peripherals, and Software. By providing a dedicated, high-speed connection between the graphics controller and main memory that matches the processing power of an Intel processor, AGP balances the overall performance of the Intel Architecture PC platform. PC OEMs can build systems that more fully realize the potential of the Intel processors, and graphics Independent Hardware Vendors (IHVs) can build products that are no longer constrained by the limited bandwidth of the PCI bus. AGP is a scalable solution designed so that graphics performance will improve with performance increases of Intel processors.
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Intel has posted a Bibliography of Impedance Compensated Driver Papers Related to AGP 4X Buffer Design on the AGP Implementors' Forum website. The papers listed in the bibliography describe various means and devices for impedance compensated output drivers. The information is intended to give designers ideas related to the design of buffers for AGP 4X. While the designs discussed in the papers are not exactly what is needed for AGP 4X, the principles for AGP drivers are illustrated. For instance, many of the papers use very low output voltages (1.0 volts) and N-MOS drivers for pull-ups as well as pull-downs; making a full CMOS driver is a simple extension to such circuits.
There are three new ECRs on the AGP Implementors' Forum website:
- ECR 43 IVDDQ
- ECR 44 3.3V VDDQ (min) change
- ECR 45 Secondary Side Keepout removal
Intel has posted an updated version of its AGP VxD with performance improvements on the AGP Implementors' Forum website; VgartD v1.0.22).
Intel is nearing completion of the final version of the AGP Interface Specification, Revision 2.0. It is expected to be available before the end of April. The final version will be posted at the same location where the preliminary draft currently resides.
On March 6, 1998 Intel announced that it is working with industry-leading workstation OEMs and graphics vendors on a new graphics specification designed to extend AGP to meet advanced workstation graphics needs. The new specification, AGP Pro, is expected to deliver up to four times the electrical power of today's AGP interface specification. It includes an enhanced connector, improved cooling system, form factor specifications such as graphics card size, and layout specifications to meet the demands of workstation graphics users on both IA-32 and IA-64™ platforms. The new specification will be supported in both AGP 2X and AGP 4X modes. Intel expects to make public the AGP Pro specification during the second quarter of 1998 as an addendum to part of the AGP Interface Specification Rev. 2.0. The Preliminary Draft of the Accelerated Graphics Port Interface Specification Rev. 2.0 is available on the internet. This specification includes the AGP 4X enhancements, in addition to incorporating the Engineering Change Requests (ECRs) from the earlier Rev. 1.0 specification.
Intel has written a Maximizing AGP Performance whitepaper and published it on the AGP Implementors' Forum website. This paper presents usage guidelines for maximizing AGP bandwidth. The paper is organized into three main sections: Data Movement, AGP Performance, and Guidelines. The first section relates platform data movement to the three different modes used to move data over AGP. The next section describes the features of each mode, and explains how these features influence the mode's performance. The last section presents guidelines for each mode along with data justifying the guidelines and examples showing the importance of following the guidelines. This paper focuses on AGP Interface Specification Rev. 1.0 performance.
In August 1996, Intel introduced the Accelerated Graphics Port (AGP) Interface Specification Rev. 1.0. The specification included information on how to design AGP products for PCs. The AGP specification only allowed for a single AGP device. This meant that the AGP device could either be soldered "down" on the motherboard or supported "up" by an AGP connector. The latter alternative enables PC manufacturers or PC users to use a variety of AGP graphics cards. However, the specification did not provide for similar flexibility in systems that used graphics "down." In an effort to support PC OEM demand and increase AGP flexibility, Intel has developed a solution that will permit an AGP alternative for those systems that were designed with AGP graphics "down." Intel has posted an ECR for AGP Rev. 1.0, and has included similar information on page 25 of the Preliminary Draft of AGP Rev. 2.0. While this new, more flexible approach will provide more options for connecting AGP devices, the specification will still allow the use of only one AGP device in each system at any given time. This specification change increases AGP design flexibility, although the solution space for the change is narrow and design implementation will require extensive simulation, testing and analysis. It is the responsibility of the PC OEM to do the extensive design, layout, and validation of each and every combination of chipset/graphics/motherboard to ensure interoperability of an upgrade solution within the specification. In short, an OEM can design a motherboard that has an AGP device soldered down on the motherboard as well as include an unpopulated AGP connector.
Intel continues with the development of its Intel Performance and Evaluation Kit (IPEAK) tools for graphics. The intent of these tools is to provide a very useful family of platform performance and integration tools to the industry to enable development of higher performance and more robust products with a quicker time-to-market. Although the final tools are targeted to be available in Q1'98, you can join the beta program today. The IPEAK Graphics Toolkit currently consists of two tools that help OEMs and IHVs analyze and improve the performance of their graphics solutions. First, The Graphics Performance Toolkit provides a better understanding of the performance issues and limitations related to graphics hardware and applications. Second, the Baseline AGP System Evaluation Suite is a system integration and validation tool that provides the capability to test and evaluate AGP system-level functionality and utilization. (For further details please visit the IPEAK web site.
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PC OEMs—When delivering high-performance PCs to your customers be sure to choose the Intel Pentium II processor and the Intel 440LX AGPset. This powerful combination will provide the necessary horsepower to meet your customers' expectations for high-performance graphics (e.g., extremely powerful floating-point performance, DIB, etc.).
Graphics Chip and Card Vendors—Design your second-generation AGP products to support the high-performance AGP features (e.g., SideBand Addressing, Pipelining, AGP 2X, etc.). Be sure to proactively design in support for AGP Texturing, in addition to Local Texturing.
Software Developers—Now is the time to develop exciting new applications that take advantage of AGP technology. Create applications with rich, lifelike textures to take advantage of the many AGP enabled PC systems and cards entering the market in the second half of '97 and throughout 1998. Take advantage of the AGP capability to use main memory as an extension to the local graphics memory (i.e., AGP Texturing).
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Visit Intel's AGP web site to download the Preliminary Draft of the Accelerated Graphics Port Interface Specification Rev. 2.0, which includes the AGP 4X enhancements.
Visit Intel's AGP home page for more detailed information on AGP and a tutorial explaining AGP functionality at the system level.
Visit the AGP Implementors Forum home page for more development, product, and event information, including registration details for the next AGP Plugfest and helpful design guides.
Visit IPEAK web site for more information on Intel's IPEAK Graphics Toolkit. Join the beta program today, with final tools targeted for the first quarter in '98.
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* Legal Information © 1998 Intel Corporation
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