Closer Look at Presler C1 Core Stepping

As you know, the first Pentium D processors based on the new 65nm core were built on Presler B1 core stepping. Compared with the previous 90nm Smithfield core that was used in older Pentium D models, the new Presler has a lot of advantages. Among them we should first of all mention higher performance due to larger overall L2 cache memory that has been increased to 4MB (2MB for each core) and lower heat dissipation that has been reduced due to finer and more advanced manufacturing process. However, the first Presler based CPU owners revealed a few noticeable drawbacks. Presler B1 core stepping processors turned out to have no Demand Based Switching support, a set of technologies that proved to be very efficient in the older Intel processors. It means that Pentium D and Pentium Extreme Edition that belong to the 900-series do not support Enhanced HALT State and Enhanced Intel SpeedStep Technology. This is exactly why Intel was in such a hurry to convince the users that this drawback would be eliminated very soon: the new core stepping supporting all the above listed technologies was promised to come out in January a month after the first Presler processors came out.

The new Presler core stepping – C1 – first of all resolved the issue with power saving and power consumption technologies. Enhanced HALT State and Enhanced Intel SpeedStep Technology have been implemented in this core stepping and work without any trouble. However, these were far not the only improvements that the new core stepping has acquired.

The CPUs with the new core stepping received another great improvement. The new core stepping allowed Intel to reduce the heat dissipation of its dual-core processors. This was a very impressive reduction that allowed Intel to move its new C1 Presler processors into a completely different thermal category. The power envelope of the new Pentium D CPUs rated from 930 to 950 will be determined by the 2005 Mainstream FMB requirements (typical heat dissipation – 95W). For your information, the previous modification of the Presler core belonged to the 2005 Performance FMB thermal envelope (typical heat dissipation – 130W).

Of course, the top Presler models from the Pentium Extreme Edition family will still beloong to CPUs with 130W thermal envelope. However, it is important to understand that the “typical heat dissipation” parameter doesn’t have any direct relation to the practical heat dissipation. This parameter serves to define the requirements the processor sets for the mainboard voltage regulator circuitry and cooling system. In other words, the heat dissipation of the Pentium Extreme Edition on the C1 core stepping will also get lower, but not greatly enough for this processor to get into the pretty numerous 2005 Mainstream FMB category.

It is important to point out that the introduction of the new Presler core stepping should not cause any compatibility issues. Presler processors with C1 core stepping are fully pin-compatible with the previous core stepping CPUs. The maximum a user may need when shifting to a CPU with the new C1 core stepping is to reflash the mainboard BIOS.

Unfortunately, it is still too early to pronounce the mass availability of the CPUs with the new Presler core stepping. Pentium Extreme Edition 965 supporting Demand Based Switching will arrive into the market on April 1, and the improved Pentium D from the 900-series should hit the shop shelves no sooner than by the end of next month.

It shouldn’t be too difficult to distinguish between the new Pentium D processors with lower heat dissipation and their older brothers thanks to a slight change that has been made to the CPU marking. Presler processors with C1 core stepping will carry the info about the 2005 Mainstream FMB category they belong to on the processor casing top: 05A.