Intel® 865G/865GV Chipset Datasheet - download.intel.nl - Intel

Functional Description5.3.1 GMCH AGP SupportTable 27. AGP Support MatrixParameter AGP 3.0 AGP 2.0 CommentsData Rate 4X or 8X 4X, or 1X GMCH does not Support AGP 2XElectricalsSignal PolarityHi / Low prioritycommandsStrobe Protocol0.8 V swing, parallelterminatedMost control signalsactive highOnly low priority(renamed Async)Strobe First – StrobeSecond Protocol1.5 V swing serialterminatedMost control signalsactive lowHigh and low prioritycommands supported.Strobe – Strobe#protocol.This change was necessary toeliminate current flow in the idlestate. Parallel termination has alarge current flow for a high level.High priority does not have a goodusage model.Long transactions Removed SupportedPIPE# support No Yes SBA required for AGP 3.0Calibration Cycle Required No New to AGP 3.0.Dynamic BusInversionYes No New to AGP 3.0CoherencyRequired for AGPaccesses outside of theaperture, and forFRAME-based accessesRequired only forFRAME-basedaccesses.5.3.2 Selecting between AGP 3.0 and AGP 2.0The GMCH supports both AGP 3.0 and limited AGP 2.0, allowing a “Universal AGP 3.0motherboard” implementation. Whether AGP 2.0 or AGP 3.0 mode is used is determined by thegraphics card installed. An AGP 2.0 card will put the system into AGP 2.0. An AGP 3.0 card willput the system into AGP 3.0 mode. The mode is selected during RESET by a hardware mechanismwhich is described in Section 5.3.3.1. The mode determines the electrical mode and can not bedynamically changed once the system powers up.5.3.3 AGP 3.0 Downshift (4X Data Rate) ModeAGP 3.0 supports both an 8X data rate and a 4X data rate. The purpose of the 4X data rate is toallow a fallback mode when board routing or other reasons make the 8X data rate marginal. SomeAGP4X graphics cards currently fall back to a 2X data rate when board layout or other issues arise.This is referred as “downshift” mode. Since AGP 2X is not supported, any card falling back to 2Xwill be running in a non supported mode. When in AGP 3.0 mode in the 4X data rate, all of theAGP 3.0 protocols are used.Intel ® 82865G/82865GV GMCH Datasheet 159