In 64-bit servers, AMD and Intel will soon be on the same page, architecturally speaking. But these similar ends were reached by very different means.
AMD carefully and selectively built on the Opteron core and total system architecture it created six years ago. In that same span of time, Intel has had to wipe its Xeon engineering slate clean twice: Once to abandon NetBurst (Pentium 4) to begin anew with a Pentium III-based CPU core called Core, and a second time to rip and replace everything outside the Core 2 core to create a completely new system architecture.
AMD's Opteron core and system design have remained intact and relevant for far longer than most interpretations of Moore's Law suggest is possible. Intel's tumultuous path to the x86 present is predictable, given the tumult that typified major turning points in x86's history. The scratch building that Intel has done in the past six years would seem to me perfectly rational, unavoidable, and even beneficial in light of Moore's Law -- were it not for the fact that AMD has lived under the same law and managed to maintain design continuity. No major component of AMD's total 64-bit server architecture has had to be remade in order to secure the platform's future.
Neither of Intel's disruptive redesigns was frivolous. Intel's need for a new core grew out of the reality that NetBurst couldn't be pushed any faster without excessive heat and poor yields. Intel's need for a new overall system design (peripheral, memory, and interprocessor buses) was born of the reality that the standard Intel bus design was a severe choke point for more efficient Core 2 CPUs. That generational race between CPU and bus is par for PCs; you could plot no course from NetBurst Xeon to the present without enormous upheaval.
Somehow AMD has managed to live under the same Moore's Law without having any element of its Opteron system architecture outpace or obsolete the rest. This is in accordance with AMD's unorthodox contract with customers, which holds that evolution of AMD's server platforms will proceed in a competitively brisk manner, but on as nondisruptive a path as possible. From AMD's perspective, its customers are its OEMs, makers of the branded servers that IT buys. OEMs love AMD's approach. Their manufacturing processes don't need to be reworked to accommodate new CPUs. AMD's OEMs are spared radical reengineering and can get new systems to market more quickly and cheaply.
In AMD's world, Moore's Law still holds sway, but it manifests differently, and the reason is simple: Opteron started with a cohesive system design, any part of which could scale without the need for replacement. AMD engineers thought through the headroom questions -- at what point will a future Opteron be throttled by its bus, and how fast can the bus be driven within noise, distance, and voltage limits?