With the 875P chipset (Canterwood), PAT is only activated when a CPU with FSB 800 is detected by the Northbridge of the chipset. This involves the signal BSEL [1:0]. The following states are shown in the table below:
[b]BSEL1 BSEL0 CPU Freq[/b]
0 0 FSB400
0 1 FSB533
1 0 FSB800
1 1 Reserved
With the 875P chipset, PAT is only switched on when the signals are BSEL1=3D1 and BSEL0=3D0 ("FSB800"). However, this function is deactivated with the 865 chipset (Springdale). Asus found a sort of "back door" for this. Although the state [1:0] is blocked on the 865 chipset (Springdale), Asus still discovered that the fast memory access PAT is kept open for the states [0:0] and [0:1], or FSB 400 and FSB 533, respectively.
Fuente: Metamorphosis from Springdale to Canterwood
Otros links de interés:
Asus: ASUS P4P800 series motherboard with HyperPath
Abit: Las Series IS7 / IC7 de ABIT, ahora con Game Accelerator