The hardware platform I am working with is equipped with an AMD SB600 South Bridge device. In the AMD Register Explorer diagnostic utility, using the SB600.rai hardware description file, I can select to examine the registers associated with any of the various integrated functions (devices). When I select the SMBus function (Bus:0 Device:20(14h) Function:0), which is assigned PCI Vendor id 0x1002 and Device id 0x4385, and press the "Access Device" button, a small "Access Device" window opens. On this window there is a drop-down box control labelled "Resource to Access:" which allows me to choose between "PCI:base=0h, size=100h" and "I/O:base=B00h, size=10h (PCI:10h=fffffff0h)". When I select the first choice I can enter an offset value of 80 and a data value of A78 into the text boxes provided, and control the value stored in the register I want. When I select the second choice, however, my attempts to change the register value seem to have no effect.
What is the difference between the first choice ("PCI:base=0h, size=100h") and the second choice ("I/O:base=B00h, size=10h (PCI:10h=fffffff0h)")? Do they point to different beginning memory locations? Do they in fact describe blocks of memory of different sizes at different locations? What does the phrase "PCI:10h=fffffff0h" mean?