What's New In The D0 Stepping?

First of all , the D0 stepping of the Intel Core i7-900 series of microprocessors comes with a slew of bug fixes. Here's a partial list of errata fixed in this stepping :

• The PECI Throttling Counter May Not be Accurate
• A Processor Core May Not Wake Up from S1 State
• A Floating-Point Store Instruction May Cause an Unexpected x87 FPU Floating-Point Error (#MF)
• Incorrect TLB Translation May Occur After Exit From C6
• Critical ISOCH Traffic May Cause Unpredictable System Behavior When Write Major Mode Enabled

On top of that, the new D0 stepping also features a slightly lower operating voltage of 1.15 V, and a correspondingly lower power consumption and thermal output. Of course, Intel maintains that nothing has changed. Officially, the two core steppings still have the same voltage ranges and TDP (thermal design power). In fact, this was Intel's official word on the new D0 core stepping :

The electrical, mechanical and thermal specifications remain within the current specifications. Intel anticipates no changes to customer platforms designed to previous Intel guidelines.

In other words, nothing has changed. Of course, we know that's not true.

It Is Also Faster!

Most hardware enthusiasts favour the D0 stepping because it not only runs cooler and uses less power, it is also more overclockable than the C0 stepping. However, most people do not know that the D0 stepping offers much more than that - it is also faster than the C0 stepping!

Intel naturally does not want you to know this because they would like you to continue buying Core i7 processors that are still using the C0 core. It wouldn't do if there's a mass rejection of their C0-based processors - the Core i7-965 Extreme Edition, the Core i7-940 and some of the Core i7-920, in favour of their new D0-based processors.

Sure, a sale of any Core i7 processor is still a sale, and they know that hardware enthusiasts will always favour a newer core, but hardware enthusiasts have always been a relatively small group. If word gets out that the new D0 core is also faster than the older core, even the n00bs might reject the C0-based processors.

Of course, this all depends on how much faster the new D0 core is, compared to the C0 core. This is exactly what we will be examining in this article. Let's find out!

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