Santa Clara (CA) - Intel is transitioning all of its 45 nm Xeon DP processors from the C-O to the E-0 stepping. There are no changes in the feature set of the Harpertown quad-core CPUs and Wolfdale dual-core processors, with the exception of the flagship model, which is the sister model of the company’s Skulltrail processor Core 2 Extreme QX9775. The thermal design power (TDP) rating of the Xeon X5482 drops by 20%.

According to a product change notification sent to Intel customers yesterday, all 18 current 45 nm Xeon processors are transitioned to the new stepping with first samples expected to become available on July 3. The updated processors are scheduled to begin shipping on October 6 and Intel asks its customers to be prepared to receive these CPUs by October 20 of this year.

Since there are no new features and (almost) no specification changes, Intel says that only "minimal re-qualification" will be required on the system builder side. However, the new chips will require a BIOS update.

The only CPU that does see specification change is the Xeon DP X5482: According to Intel, the 3.2 GHz chips carries a 120 watt TDP rating in the E-O stepping, compared to a 150 watt rating in the C-O version. The current Skulltrail processor Core 2 Extreme QX9775 is also clocked at 3.2 GHz and rated at a 150 watt TDP.

We don’t know whether the power consumption of the processor in fact drops, or if the new TDP rating is simply a bit closer to reality. According to a review posted by Tom’s Hardware, a Core 2 Extreme QX9775 consumes a maximum of 114 watts at 3.2 GHz. The power consumption climbs to about 138 watts when overclocked to 3.6 GHz and 176 watts at 4 GHz.

But enthusiasts who are interested in building a Skulltrail PC should have a closer look at Harpertwon processors - and not just because of the upcoming stepping update: Even the pricey X5482, which currently lists for a tray-price of $1279 per piece and sells for about $1400 in retail, is substantially cheaper than the QX9775, which has a tray-price of $1499 and sells for closer to $1700 per CPU in retail. Even if you are sinking more than $10,000 into a Skulltrail PC, a few hundred dollars of savings aren’t bad.