About a year ago, Intel’s latest sibling, the Pentium 4, was introduced with lots of media attention and it was pitched as a CPU that was designed for high bandwidth streaming content and multimedia applications. As such the Pentium 4 had one of fastest memory subsystems ever found in a PC, it featured dual channel Rambus with an impressive 3.2GB/s of bandwidth. The whole NetBurst architecture that debuted with the Pentium 4 and the i850-chipset’s launch was meant to do away with many of the bottlenecks found in previous CPUs, motherboards and chipsets. It featured a number of improvements that made sure the Pentium 4 was fed with enough data to keep it running efficiently.
Fig 1. Intel's i850-chipset, featuring the NetBurst architecture and dual channel RDRAM with 3.2Gb/s of bandwidth.
However from a price/performance point of view the new Pentium 4 looked a lot less impressive. AMD’s Athlon offered comparable, or better, performance, at a much more affordable price, something that must have caused enough concern at Intel to start thinking about reducing the cost of the Pentium 4 platform. While the Pentium 4 CPU has seen massive price cuts, an i850-chipset based Pentium 4 platform still comes at a price premium, partly due to the use of PC800 RDRAM. To further reduce cost, Intel introduced the i845-chipset a few weeks ago which is a new Pentium 4 chipset supporting SDRAM.
Fig 2. Intel's i845-chipset also featuring the NetBurst architecture but utilizing PC133 SDRAM as a memory subsystem.
With current SDRAM pricing, outfitting an i845 Pentium 4 platform with 256 MB of quality PC133 memory will cost you in the neighborhood of $60. Outfitting an i850 Pentium 4 platform with 256MB, which would require two 128MB PC800 RIMMs, will cost you twice that. Considering the lower price of SDRAM and taking into account the lower price of the i845-chipset Intel has indeed found a way to bring down the cost of the Pentium 4 platform. I845-chipset based Pentium 4 systems of similar clockspeed should on average be $75 cheaper than their i850-chipset based counterparts.
However wasn’t the whole high-bandwidth, low-latency NetBurst architecture of the Pentium 4 and the performance resulting from it based on having plenty of memory bandwidth? The i845 clearly has to do with a lot less memory bandwidth as PC133 SDRAM has about 1/3 the bandwidth of dual channel PC800 RDRAM. What drawbacks come from utilizing SDRAM for a CPU that needs a high bandwidth memory subsystem to perform? In the next few pages we’ll be investigating whether the i845 is worth saving a few dollars on your purchase or whether you should steer clear of the i845 altogether.