We have reported on previous stories how motherboard manufacturers have been enabling Intel's Performance Acceleration Technology (PAT) on mainstream i865 based motherboards through BIOS updates while this feature was really only meant to be available in higher-end and more expensive motherboards that are equipped with 875 chipsets.
x86-Secret has just published an article on the PAT technology (found through W2S) that comes to confirm all the information heard these last days. On the contrary of what Intel is stating, PAT is present on ALL i865 and i875 chipsets and is moreover activated by default on these 2 chipsets for all modes less than FSB800/DDR400. However, the i875 is the only one to keep PAT activated in FSB800/DDR400 mode due to a better chip quality. Manufacturers like AsusTek, followed by others these last weeks, have found a workaround for the i865 chipset by making it believe that the CPU is at a 533 FSB setting, even when it's at FSB800.