Anyway, I am really stumped by such news since such CPU upgrade is really a very common thing in the PC world, so I guess, this isn't much the case with Apple world. So anyway, their adventure went on from getting a Mac* with a stock Intel® Core® Duo 1.83Ghz. Then, the author of the mag, decided to get a new Intel® Core® Duo 2.0Ghz, and replaced the CPU. The system booted up just fine, and even reported the correct speed of the new CPU. Well, sounds really boring to me, but I guess in the Macworld, this is a whole new ballgame for them. So I guess it's all good.
As promised in a preceding news, w00kie, who's in Japan, got hold of the Macfan article.
The journalist states he bought a Core Duo 2 GHz CPU in a PC shop and installed it in his machine in place of its 1.83 GHz.
The machine booted flawlessly and system information displayed the right 2 GHz frequency.
Here are some explanations about how this can be.
A CPU frequency is related to two parameters, the bus frequency, and the multiplying coefficient of the CPU.
On G3s and G4s, the easier way for overclocking was to modify the multiplying coefficient. Yet to prevent such a manipulation, Intel, and then AMD, locked those coefficient setttings directly inside the CPUs. That's why overclocking of X86 CPUs require modifying the system bus frequency.
So, as any other CPUs, the Core Duo have a locked coefficient. The system bus of those machines is at 166MHz (x4 = the announced 667). The original CPU had a coefficient locked to 11. The 2 GHz one is locked at 12.
That's why the simple fact of changing it allowed to reach the right, reference frequency, without any further modification.
The real good news is that Apple didn't find useful to add a lock inside the EFI in order to prevent a potential upgrade.
Whether changing the CPU will not result in a noisier machine, because of fans turning faster, still remains to be seen.
From an anecdotic point of view, a 2 GHz Core Duo costs about 480 Euros in France, while the 2.16 GHz version costs over 700. The game is clearly not worth it yet. It will take several months for those prices to drop significantly.