M1543C B1 : South Bridge M1543C : South

Built-in PCI IDE Controller
· Supports Ultra 66 DMA Mode Transfers up to Mode 4 Timing (66 Mbytes/sec)

Built-in PCI IDE Controller
· Supports Ultra 33 DMA Mode Transfers up to
Mode 2 Timing (33 Mbytes/sec)

The major differences between M1543C B1
and M1543C A1
Ÿ M1543C B1 supports Ultra DMA 66 feature
The Ultra 66 needs two input pins for cable
selection. At M1543C B1x, SD_GPIO[5:4]
can be used as input pins for cable selection.
SD_GPIO[4] is used for primary channel and
SD_GPIO[5] is used for secondary channel.
Use M1543C B1 x CFG index 79h bit 2 as enable bit :
0 : Disable SD_GPIO[5:4] as cable selection.
1 : Enable SD_GPIO[5:4] as cable selection.