What's the meaning of AMD CPU steppingC0,CG,D0?

[mailrapid]

AK Stepping C0, CPUID 5, single core, 0.13 micron, socket 940
AP Stepping C0, CPUID 4, single core, 0.13 micron, socket 754
AR Stepping CG, CPUID 4, single core, 0.13 micron, socket 754
BI Stepping D0, CPUID 1F, single core, 0.09 micron, socket 939

I don't know the meaning from message shown above, could you please help me to answer?
1. What's the meaning of stepping C0,CG,D0?
2. What's the meaning of CPUID 5,4,1, from which we can know...?

 

[rammedstein]

stepping is the "version", cpuid is the identifier for everything on the cpu (cpu has the cpuid, mobo has cpuids and a list of settings ect, when it detects the chip it puts the appt cpu settings in of the chip, other ways of doign it too)

 

[dragonsprayer]

google the stepping and see the changes - almost every time they improvemnts. microcode changes, bios fixes or better throttling