Register 88
3,2,1,0 set the CPUs multiplier Both Register 88 and 89 have settings for this.
Register 8B
0 = AMD Athlon Bus Threshold 0=1.35-1.9V 1=2.0-2.2V
I'm not finding any really helpful data on this setting but anytime something talks about a higher voltage it gets my attention. I believe this was most likely included in the chipset with future processors in mind. I have not seen any motherboards support higher than 1.9v but using this I wasn't able to do a software
AGP Status A4, A5 just tell you that the chipset supports these features.
Register A8
4 = Fast Writes Enable 0=disable 1=enable you'll have to set a register in B4 also to properly enable Fast writes
2,1,0 = AGP mode 4x,2x,1x are options. Since each one is also backwards compatible with 4x all 3 settings will be set to 1 which is enabled.
Register A9
1 = Sideband Addressing 0=disable 1=enable
Register B9
7 = Fast Writes Override 0=disabled 1=enabled fast writes will only be properly enabled if this setting and the FW setting in A8 are properly set.
6 = Force AGP 4x If you're having any problems getting 4x to work properly for you you'll want to set this to 1