Macs are seldom compared to Athlon/Pentium platforms for the same reason the latter aren't compared to Itanium platforms.
Different architecture.
PowerPC and Itanium use RISC (Reduced Intruction Set Computing) architecture, where Athlons and Pentiums use CISC, or x86.
The RISC architecture is generally more efficient than CISC, especially from a power usage point of view, mainly because they are much simpler.
As for application-specific comparison between the three CPUs (Athlon/P4 vs G5), Intel and AMD are only able to compete through sheer muscle (Mac simply doesn't have the resources).
The performance gains associated with RISC are the reason Intel wanted to move its entire line away from x86.
I cannot help but postulate that had AMD/Intel moved to RISC, we would very likely be seeing much, much higher performing, not to mention cooler, CPUs.
Different architecture.
PowerPC and Itanium use RISC (Reduced Intruction Set Computing) architecture, where Athlons and Pentiums use CISC, or x86.
The RISC architecture is generally more efficient than CISC, especially from a power usage point of view, mainly because they are much simpler.
As for application-specific comparison between the three CPUs (Athlon/P4 vs G5), Intel and AMD are only able to compete through sheer muscle (Mac simply doesn't have the resources).
The performance gains associated with RISC are the reason Intel wanted to move its entire line away from x86.
I cannot help but postulate that had AMD/Intel moved to RISC, we would very likely be seeing much, much higher performing, not to mention cooler, CPUs.