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Now that Intelís legal obligations to Rambus have expired, Intel has been hard at work at bringing DDR memory support to the Pentium 4 platform. Things kicked off with the 845D chipset at the beginning of this year. You may not realize this, but 845D was actually launched unofficially in 2001 when the 845 chipset originally debuted. You see, 845 and 845D share the same memory controller, all Intel did was disable the DDR functionality that was already present in the chipset. Motherboard manufacturers were displaying their DDR 845 motherboards as early as at Computex last June, and at Comdex in November 2001. So once Intel was able to release its DDR variant of 845, motherboard manufacturers had no problems getting their respective products to market.
When Intel unveiled its 533MHz Pentium 4 bus, they also released a companion DDR chipset that supported the new bus speed, 845E. Besides offering official support for the 533MHz Pentium 4 processors, 845E didnít bring much additionally to the table. Sure, we got USB 2.0 support via the ICH4 South Bridge chip, but PC2100 (DDR266) was the fastest memory type supported.
The bandwidth limitations of DDR266
With the 533MHz Pentium 4 bus offering the processor up to 4.2GB/sec of bandwidth, the 2.1GB/sec limitation of DDR266 was leaving the Pentium 4 starving for more bandwidth. We saw this in our SiS 648 preview, where its DDR333 (and unofficially DDR400) memory was much more capable of satisfying the Pentium 4ís bandwidth needs. In our testing it performed roughly eight percent faster than 845E in most applications.
As a result, many of those in the know simply overclocked the bus on their 845D motherboards to 533MHz and accepted the fact that they were left with only DDR266 memory support. They may have been stuck with the outpdated performance DDR266 memory provided, but at least they wouldnít have to shell out their hard-earned dollars for a new motherboard based on the 845E chipset. Some enthusiasts left the Intel chipset entirely and opted instead for one of SiSís DDR offerings for the Pentium 4: SiS 645, SiS 645DX, or, more recently SiS 648.
Today Intel is back again with two new chipsets that officially bring DDR333 memory support to the table. With any luck they may provide a solid alternative to going the SiS route. Lets see how they shape up!