Refinements and performance optimizations in PC motherboard designs often track chipset re-spins and tweaks, as a new base architecture matures. Intel is absolutely famous (or shall we say infamous) for releasing a new chipset only to set sail with a re-spin or further characterization of the product, just a few months later. Such was the case for Intel's i925X chipset.
PC Motherboard OEMs first to market with new i925X "Alderwood" offerings are now trying to shift gears and react to Intel's characterization and branding of the chip at 1066MHz Front Side Bus speeds. The i925X now has an "E" revision denoting "official" support for this new higher speed system bus, only its the exact same die in that Northbridge package, just validated to perform at 1066MHz.
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