It's the same chip and same technology. The process at which they are made mature over time, hence the same part with a lower TDP.
Again, the Xeon 5365 were still first officially released in August.
If chips were available before that they were OEM and not retail. In fact, I still have trouble finding retail Xeon 5365 in Denmark.
Here, I'll quote the link that I posted - since apparently it didn't work for you:
http://www.dailytech.com/New+Intel+Xeon+Steppings+on+the+Way/article7630.htm
Intel Xeon 5100 and 5300 receive minor enhancements
Intel has issued a new product change notification (PDF), or PCN, to partners in regards to dual and quad-core Xeon stepping changes. The stepping change brings the dual and quad-core Intel Xeon 5100 Woodcrest and 5300 Clovertown processors to stepping G0.
G0 introduces energy efficiency and virtualization enhancements.
Stepping G0 reduces power consumption during C1E halt states. Intel does not state how much less power stepping G0 processors consume in idle states except “some amount.” Intel improves VT technology in stepping G0.
The enhancements include:
- APIC Task Priority Register (TPR) Virtualization
- NMI-window exiting
- Advanced VM-exit information for INS & OUTS
All stepping G0 processors will receive new CPUIDs. The Clovertown CPUID will change from 06F7 to 06FB while Woodcrest changes from 06F6 to 06FB. Stepping G0 processors will also receive new SSPEC numbers.
Stepping G0 processors will require a BIOS update with new microcode for proper identification. However, with the proper microcode update, users should be able to mix and match processor steppings in multi-processor configurations.
The 150-watt B3 stepping that Apple is using is an evolution in process. As the process matured, sufficient numbers of chips that would reliably run at 3 GHz were being produced, and Intel offered those to its customers. Apparently most of the customers decided to say "no" and wait for the improved G0 chips.
The 120-watt G0 stepping is a different chip - there are changes in the logic circuits. Most of the logic is identical to the older 150-watt chips, but there are some changes. It has new features, and consumes less power. Some of the improvements are real logic changes, and others are a result of creating a new mask and tweaking the process with the new mask. Sometimes you need to modify the chip to capitalize on process improvements.
In some sense a chip is a "photograph" created with a certain process - and a "stepping" is a change in the "negative" to make a better "photograph".
As I said - "Don't be confused that both are called X5365 - the 150 watt chips are older technology". They can be the same process, and still be older technology.
After all, this whole thread is about the FrankenMac - old technology at new prices.