A new chipset is available for the Pentium 4 processor with 533MHz frontside bus (FSB) -- the P4X333 from VIA. Whereas Intel’s 850E supports Rambus memory, the VIA P4X333 uses 333MHz DDR memory (DDR333). Although VIA’s legal battle with Intel continues (this concerns missing licences for the Pentium 4, which Intel claims are needed in order to sell P4-certified chipsets), VIA is now delivering its new P4X333 chipsets to motherboard manufacturers. However, because of Intel’s threatened repercussions, few vendors are yet using the P4X333. Therefore, VIA has gone into the motherboard business itself, and has recently begun delivering its own boards. Intel 850E The new 2.26, 2.4 and 2.53GHz Pentium 4 processors require chipsets that support a 533MHz FSB. Intel’s main offering for performance-orientated PCs is the Rambus 850E chipset (recently, Intel has released two 533MHz-compliant DDR chipsets, the 845E and the 845G, but these do not support the latest DDR333 memory). The 850E’s memory clock remains officially unchanged at 400MHz. Some motherboard vendors also support the new 533MHz PC1066 Rambus memory, and Intel’s D850EMD2 and D850EMV2 boards do function with PC1066 memory. However, this is outside the official specification, so you can expect little support if you run into problems. The combination of the Pentium 4’s 533MHz FSB and the new PC1066 Rambus memory delivers a big increase in the bandwidth of the memory subsystem. Bus bandwidth between CPU and memory rises to 4.2GB/s, and with PC1066 memory this transfer rate can actually be achieved. When slower PC800 memory is used, the memory transfer rate is limited to 3.2GB/s. Even when PC800 memory is used, CPU performance increases compared to the previous 400MHz-bus 850 chipset, because Intel has integrated mechanisms into the 850E’s buffer that minimise the number of accesses to the memory. However, performance with the more efficient PC1066 memory is higher still, because the chipset buffer cannot intercept all of the memory accesses.
VIA P4X333 With the P4X333, VIA has delivered some innovative features. Besides 533MHz bus support for the Pentium 4, there's a new graphics interface based on the AGP 8X standard. Although there are no 8X-compatible graphics cards available on the market yet, nVidia’s GeForce4 graphics chip is AGP 8X-compatible. VIA has also integrated support for DDR333 memory into the P4X333, delivering a maximum data throughput of 2.7GB/s. However, the FSB bandwidth is 4.2GB/s. VIA tries to reconcile this inequality by using buffer technology in the Northbridge -- and it seems to very successful, as our memory benchmarks show.
How we tested The test systems were all equipped with 256MB of memory -- DDR CAS2 with the P4X333, PC800 and PC1066 Rambus with the 850E. The hard drive was an IBM DTLA 30730, which was driven by the motherboard’s EIDE controller. With the Intel board, the newest version of the Intel Application Accelerator (IAA) was installed. The P4X333 board from VIA used the latest VIA EIDE driver. The graphics subsystem was the Asus V800 T5 with nVidia’s GeForce 3 Ti 500 chipset and the Detonator driver version 22.80. All tests were carried out using a 2.53GHz Pentium 4 processor running Windows XP. Memory performance