Notice: Undefined index: article155 in /www/hardwaresecrets/article.php on line 5 AGP Bus Tutorial | Hardware Secrets
Hardware Secrets
Home | Camera | Case | CE | Cooling | CPU | Input | Memory | Mobile | Motherboard | Networking | Power | Storage | Video | Other
Content
Articles
Editorial
First Look
Gabriel’s Blog
News
Reviews
Tutorials
Main Menu
About Us
Awarded Products
Datasheets
Dictionary
Download
Drivers
Facebook
Links
Manufacturer Finder
Newsletter
RSS Feed
Test Your Skills
Twitter
Newsletter
Subscribe today!
Recommended
AGP System Architecture (2nd Edition)
AGP System Architecture (2nd Edition), by Tom Shanley (Addison-Wesley Professional), starting at $0.50


Home » Motherboard » Bus
AGP Bus Tutorial
Author: Cássio Lima 149,846 views
Type: Tutorials Last Updated: June 23, 2005
Page: 1 of 3
Introduction

Until the release of the AGP bus, video cards were installed in the PCI bus. The maximum theoretical transfer rate of the 32-bit PCI bus at 33 MHz was 133 MB/s, an insufficient rate for 3D applications (such as games, for instance) and that limited the development of more sophisticated video cards. Besides of its low transfer rate, the PCI bus had another problem: it was ”choked“. The chipsets architecture used at that time was that of bridges, which used the PCI bus for the communication of the north bridge circuit with the south bridge one. Besides, most on-board peripherals of the PC were installed in the PCI bus, such as the on-board IDE ports, the SCSI controller, the on-board video, sound and network cards. No to mention the peripherals that could be installed in the PCI bus via PCI slots.


click to enlarge
Figure 1: Simplified diagram of the PCI bus.

It happens that the maximum transfer rate of the PCI bus – 133 MB/s – is shared by devices connected to the bus, and not used by each peripheral during its transfer. In other words, the transfer rate used by a PCI video card is not 133 MB/s, but lower, for the more peripherals plugged to the PCI bus, the lower will the real transfer rate obtained by them be.

Motivated by those reasons, Intel launched the AGP bus. The main aim of the AGP bus was to increase the transfer rate of the video cards – having them installed in the faster AGP bus and no longer in the PCI bus. Technically speaking, AGP is not a bus, for only one device is connected to it: the video card. It is more a high performance point-to-point connection used only by video cards.

Intel launched the first version of the AGP (Accelerated Graphics Port or Accelerated Graph Port) bus in July, 1996. That bus worked with a clock of 66 MHz transferring 32 bits at a time, it was fed with 3.3V and operated in two modes: 1x and 2x. The first chipset to support such bus was the Intel 440LX, marketed in August, 1997.

In May, 1998, Intel launched the second version of the AGP bus that allowed the operation mode at 4x and was fed with 1.5V. The first chipset to support the second version of the ACP bus was the Intel 815P, marketed in June, 2000.

The most recent version of the AGP bus is the third one, developed in November, 2000. Actually it is an enhancement of the second version, allowing the operation mode at 8x. The first chipset to support the third version of the ACP bus was the Intel 865P, marketed in May, 2003.

Version

Operation Modes

Voltage

AGP 1.0

1x and 2x

3.3v

AGP 2.0

1x, 2x and 4x

1.5V

AGP 3.0

1x, 2x, 4x and 8x

1.5V

Print Version | Send to Friend | Bookmark Article Page 1 of 3  | Next »

Related Content
  • Inside Intel Nehalem Microarchitecture
  • Introduction to Wireless USB (WUSB)
  • Everything You Need to Know About The QuickPath Interconnect (QPI)
  • Arctic Cooling Accelero Twin Turbo VGA Cooler Review
  • Getting Educated on the Status of PCI-E 3.0

  • RSSLatest Content
    ASRock Z97 Anniversary Motherboard
    December 16, 2014 - 4:27 AM
    Gigabyte H81M-S2PH Motherboard
    December 12, 2014 - 3:05 AM
    Aerocool Dead Silence Case Review
    December 2, 2014 - 3:00 AM
    NZXT S340 Case Review
    November 27, 2014 - 3:45 AM
    AMD A4-5000 CPU Review
    November 26, 2014 - 3:10 AM
    Samsung Galaxy Note Pro 12.2 Tablet Review
    November 25, 2014 - 3:00 AM
    ASUS X99-PRO Motherboard
    November 5, 2014 - 3:00 AM
    ASRock QC5000-ITX Motherboard
    November 4, 2014 - 3:00 AM
    Gigabyte X99-UD3 Motherboard
    October 30, 2014 - 8:30 AM







    © 2004-14, Hardware Secrets, LLC. All rights reserved.
    Advertising | Legal Information | Privacy Policy
    All times are Pacific Standard Time (PST, GMT -08:00)