NVIDIA nForce4 SLI (Intel Edition) Architecture
NVIDIA nForce4 SLI (Intel Edition) chipset is designed as a traditional dual-chip solution. Although its predecessor, nForce4 for Athlon 64 processors boasted single-chip architecture, NVIDIA decided not to add the memory controller into the same chip. This way, the chipset North Bridge of NVIDIA nForce4 SLI (Intel Edition) called System Performance Processor (SPP) is a combination of the memory controller, processor interface and PCI Express bus controller. The South Bridge also known as Media and Communication Processor (MCP) ensures that the chipset support Serial ATA, network capabilities, PCI busses, integrated sound and USB busses.
The North and the South bridges of the chipset are linked together with the Hyper Transport bus, which is not so typical of the Pentium 4 platforms. This bus works at 800MHz frequency and provides 1.6GB/s bandwidth in each direction. Actually, NVIDIA has been using this bus to connect the chipset bridges since the times of the first nForce chipsets that is why it is not at all surprising that the new NVIDIA nForce4 SLI (Intel Edition) has this bus too.
I would like to point out one very curious detail here. The South Bridge of the nForce4 SLI (Intel Edition) is very similar to the single-chip nForce4 for Athlon 64 systems. The only difference between these two chips is the absence of the PCI Express bus controller in the MCP, which has been moved to the North Bridge of the nForce4 SLI (Intel Edition) to ensure better and more efficient communication between the expansion cards, CPU and memory. So, the defective South Bridges that cannot be used for Athlon 64 nForce4 Ultra may actually suit as South Bridges for the Pentium 4 chipset.
Anyway, right now NVIDIA makes MCPs individually: these are the chips consisting of 21 million transistors and manufactured with 0.15micron production process. The North SPP Bridges are manufactured with 0.13micron technology and consist of 61 million transistors.
We should also say a few words about the features of the nForce4 SLI (Intel Edition) North Bridge, as it is exactly the one bearing all the specific peculiarities of the new solution. Due to SPP, NVIDIA抯 new core logic supports any LGA775 processors with the bus working at 533MHz, 800MHz and 1066MHz. NVIDIA solution supports DDR2 SDRAM, although you can use not only the regular DDR2-400 and DDR2-533 SDRAM, but also DDR2-667 SDRAM with higher bandwidth.
As for the PCI Express bus support, nForce4 SLI (Intel Edition) is absolutely identical to nForce4 SLI for Athlon 64. In other words, there are 20 combinable PCI Express lanes implemented in the chipset North Bridge for more optimal work with two graphics cards at a time. This way, nForce4 SLI (Intel Edition) will have SLI mode working just the same way as it does in Athlon 64 systems: through two PCI Express x8 busses. And as for the pair of simultaneously existing fully-fledged x16 PCI Express busses, it remains the prerogative of NVIDIA抯 professional solutions.
