The introduction of the Intel LGA775 platform line has brought with it many changes, such as a new processor package, DDR2 memory, PCI Express graphics and peripherals, an upgraded onboard audio and video selection, and the transition of Serial ATA from a niche market into the mainstream. The Intel chipsets come in a few different flavors, with the 925X taking over the enthusiast end of things, while the 915P and 915G cater to the mainstream market. In this review we'll be comparing the features and performance of the 925X and 915G Express chipsets, as well as seeing how the newest Intel integrated graphics core stacks up in the gaming arena.
The 925X Express chipset sits at the very top of the Intel desktop line, and is the natural upgrade from the current i875P. The basic architecture also remains mostly unchanged, with the 925X sporting a dual-channel memory controller and an 800 MHz CPU bus, but the platform changes are in the type of hardware supported. The 925X Express upgrades memory support to DDR2-533, which has a whopping 8.5 GB/sec. of bandwidth. The 925X also includes a feature Intel calls "Enhanced Memory Pipelining", which is the PAT-equivalent to the 925X Express, and gives it a bit more juice than the 915-based platforms. The 925X Express also uses only DDR2 memory, and offers ECC support as well.
The 925X Express uses the new LGA775 processor package, which features 775 pins, but switches the conventional design. Instead of the CPU having pins that fit into the motherboard socket, it's the other way around, and the CPU is now the "female" in the relationship. The processor support remains consistent with the current Pentium 4 line, including 800 MHz front-side bus and Hyper-Threading support. Other than the package used, the CPU support end is pretty standard, although this could change with an upgrade to faster CPU bus speeds. The only problem is that by using an 800 MHz front-side bus, the Pentium 4 only requires 6.4 GB/sec. of matching bandwidth, so roughly 2 GB/sec. of memory bandwidth could go unused.
The dedicated video architecture has also moved to PCI Express, and Intel is standing firm that the LGA775 platforms move away from AGP and fully embrace PCI Express. PCI Express x16 Graphics provide a nice bandwidth boost over AGP, and can handle up to 8.0 GB/sec. of dedicated video bandwidth. PCI Express also provides an additional power rail for higher-end video cards, although the real enthusiast level products like the GeForce 6800-based cards still require an external power connector.
The 915G (and 915P) Express chipsets represent the mainstream LGA775 platform line, and are the next-gen upgrades to the Intel 865G and 865PE models. The new line is also similar to the 865-based structure, with the 915P offering mainstream performance with dedicated PCI Express X16 video, while the 915G offers the same mix, but with an integrated graphics core.
Much of the architecture and many of the features remain consistent between the 925X and 915G Express chipsets, such as the LGA775 socket design, support for the 800 MHz front-side bus, Hyper-Threading, and PCI Express x16 graphics, but there are some important differences. The memory architecture is similar, and features a dual-channel memory controller, but the 915G supports both DDR2 and DDR memory. This gives the platform a more mainstream appeal, and some motherboard vendors have even designed dual-memory boards, which can use DDR now and potentially upgrade to DDR2 later.
The integrated graphics core has been given a total overhaul, and the new Intel Graphics Media Accelerator 900 (GMA 900) represents a serious upgrade to the previous Intel Extreme Graphics 2 core on the i865G. The GMA 900 features a 333 MHz graphics core with 4 pixel pipelines, and support for DirectX 9 hardware acceleration, along with OpenGL. The DirectX 9 hardware acceleration part only extends to the Pixel Shaders, while Vertex Shaders and T&L are handled by the processor. The features also stretch well past the gaming arena, including better 2D image quality, DVD acceleration, and dual-monitor output through an optional add-in card.
The memory system utilizes onboard memory for the GMA 900, using Intel's Dynamic Video Memory Technology 3.0. This dynamically allocates memory depending on the scenario, and can use system memory up to a 224 MB maximum. For example, when loading a game, the GMA 900 will allocate a section of system memory, and then once the program is unloaded, this is put back into the memory pool. The actual bandwidth of dual channel DDR2-533 looks to have some in reserve for the GMA 900 video, but data contention is still a prime issue with any integrated video solution.