The B0 Stepping

The majority of these ES-related problems involve the B0 stepping. These are supposed to be the initial production test samples in which some functions were either not working properly or disabled. Most notable are the C1E and SpeedStep features, which are not properly implemented in the B0 stepping. With that said, the same problem can apply to other core steppings as well. For those who are not familiar with these features, here's a short primer.

SpeedStep

The Enhanced Intel SpeedStep Technology (EIST) allows the system to dynamically adjust processor voltage and core frequency. This can result in decreased average power consumption and decreased average heat production.

This technology is based on the proper detection of the processor's voltages and frequencies using CPU-ID to determine its VID (Voltage IDentification). The VID is a code supplied by the processor that determines the reference output voltage that the motherboard needs to supply to it. The processor can then dynamically adjust the voltage and frequency according to the processing needs.

This processor feature works hand-in-hand with the operating system through ACPI, which is one of the main reasons why Intel mandated that the Core 2 processor will require at least an Intel 965 or 975 chipset to support it. However, some of the other chipsets are also able to boot the Core 2 processors if they comply with the Voltage Regulator-Down 11.0 PWM specifications.

Interestingly, there have been reports that the Intel 975BX Rev. 3.04 motherboards can boot up B0 steppings of the Core 2 ES processors. In comparison, the Intel 975BX2 motherboard will generally not boot up with any ES processor whether it is a B0 or B1 stepping, although some lucky blokes have managed to do so. Therefore, luck appears to play a role in determining if your ES processor will boot with these motherboards.

C1E

The C1E enhanced halt state works by lowering the multiplier of the processor to achieve a lower clock speed and lower power consumption. Intel Core 2 processors work between the range of two multipliers. For example, the Core 2 Duo E6400 works between the multipliers of 6 and 8. This is much like the C1 halt state, which is used on all modern processors and triggered when the operating system's idle process issues a HLT command. Here's an explanation of the C1E enhanced halt state by charge-n-go :

In both mobile and desktop Core 2 processors, there are a few sleep states - C0, C1, C2, C3 and C4. The desktop processors (e.g. Conroe, Allendale, Woodcrest) support C0 and C1E while the mobile versions (e.g. Merom) not only support C0 and C1E but also extra states like C2 to C4. C0 is the performance state, whereas C1 is the HALT state.

Traditionally, SpeedStep occurs in the C0 state, where it dynamically changes the Multiplier and VID based on a pre-defined table inside the CPU. This is how the processor frequency and voltage changes according to CPU load.

In the Pentium 4 processor, the C1 state only calls the HALT instruction to stop the execution units and its pipeline. However, the registers, external bus logic and cache are still working at full clock speed and voltage.

In order to bring down the leakage current and idle power, C1E was introduced by combining C-states and SpeedStep. So, during C1E, the execution pipeline is halted and the clock speed and voltage are throttled to the lowest possible value (6x multiplier with lowest supported Vcore).

Now, both C1E and SpeedStep work hand-in-hand. If either one of these functions are not working properly, the VRM (Voltage Regulator Module) might not be able to determine the proper boot-up voltages and hence prevent the system from booting up. Even if you are able to boot up, Enhanced Halt State might not work properly, as noted by Intel here. So, if you are using an ES processor, do check using Intel's Processor Identification Utility.

Why Bother?

Now, some of you may be thinking, "Blah... blah... blah… What a load of mumbo-jumbo. Those two functions can't be THAT important. After all, my ES processor works perfectly fine in my system." Well, many of these engineering samples do work, in a fashion. They wouldn't be selling so well if they all didn't work at all.

However, one of the main improvements in the Core 2 processor is its much reduced power consumption. That is a big deal these days, even for desktop users. Who doesn't want a cooler processor that uses less power? But how can the Core 2 processor achieve its lower power consumption, if the two critical functions needed for that are not working right, or disabled?

While the Core 2 processor undoubtedly has better performance than the Pentium 4 processor, its greatest benefit for general users is its much greater efficiency. It does more work at a lower clock speed, with lower power consumption and lower thermal output than its predecessor. It would be a real shame if you do not benefit from these Core 2 features.

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