The AGP bus on a PC can typically run at a number of different speeds, with the slower speeds being fallback settings...
to allow better compatibility with older hardware or software. AGP systems can typically run at 1x, 2x, 4x or 8x speed; older AGP busses usually only go up to 2x or 4x. The default speed (or available range of speeds) is usually set in BIOS, and it's possible to determine the current AGP bus speed by running a software utility that polls the system.
What's confusing is if you run the utility and get a report that says, in all seriousness, that you're running at "0x" speed. I ran into this when updating a system that used ATI's Catalyst video software, which reported the AGP speed in this fashion and wouldn't allow me to set the bus speed manually at all.
This problem can manifest itself if you're on a system that has an AGP chipset driver which is buggy or out of date. In my case, I was running an AMD dual Opteron, with an AGP driver supplied specifically by AMD. (In other words, it wasn't refreshed by Microsoft Update). Said driver was dated 2002. Yes, it was four years out of date.
A more recent version, dated 2005, was available from AMD's Web site. After installing it and rebooting, not only did Catalyst start reporting the AGP bus speed correctly, but the system as a whole also began running noticeably faster.
Another possible factor is the BIOS itself, which may misreport the AGP bus speed if it's an older revision. Check to see if your BIOS needs updating, and make sure to follow the manufacturer's directions for clearing the CMOS after flashing (usually by changing a jumper setting) to avoid problems with stale CMOS data being read by the new BIOS.
About the author: Serdar Yegulalp is editor of the Windows Power Users Newsletter, which is devoted to hints, tips, tricks, news and goodies for Windows NT, Windows 2000 and Windows XP users and administrators. He has more than 10 years of Windows experience under his belt, and contributes regularly to SearchWinComputing.com and SearchSQLServer.com.
More information on this topic:
- Tip: Fast Guide: PCI bus
- Topics: Busses
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