Intel's latest motherboard chipsets, previously codenamed Alderwood and Grantsdale, are aimed at high-performance motherboards and designed to work primarily with new and repackaged Pentium 4s ranging from the Pentium 4 520 at 2.8GHz to the P4 560 at 3.6GHz. All come with 1MB of Level 2 (L2) cache and an 800MHz frontside bus; there's also a repackaged Extreme Edition part. All are housed in a new Leadless Grid Array LGA775 package. This presents the chip's connections as a grid of conductors flush with the bottom of the case -- a technique previously used on the Pentium II core.
Intel's new LGA775 package presents the Pentium 4's connections as a grid of conductors flush with the bottom of the case.
925X and 915G/P chipsets
Alderwood and Grantsdale -- more properly, the Intel 925X and the 915G and P Express Chipsets -- introduce a set of upgrades and new features. Most are shared across the family: PCI Express, 800MHz frontside bus, dual-channel DDR2 533MHz memory support, integrated Gigabit Ethernet, four serial ATA and eight USB 2.0 ports, and Intel's High Definition Audio. The 925X supports ECC memory, unlike the 915 chips, while the latter work with a selection of older Pentiums and slower memory options. The 915G also includes integrated graphics, Intel's new Graphics Media Accelerator 900, and the chips include some high-level support for wireless access points (although the wireless network adapter itself isn't included).
The 925X chipset supports ECC memory, unlike the 915G (with integrated graphics) and 915P parts.
The chipsets support legacy PCI as well as four PCI Express (PCIe) x1 'lanes' (a lane is a single uncontended bidirectional 500MB/s bus running around 6.5 times faster than PCI). Intel has dropped AGP in favour of PCI Express x16. This combines 16 PCI Express lanes into one slot, together with 75 watts of available power. With 4GB/s available simultaneously in both directions, PCI Express x16 has around four times the total bandwidth of AGP 8X and is the performance graphics bus of choice for the next generation of PCs. Intel claims it can render four simultaneous 720-line high-definition TV images at 50 frames per second (fps).
The 915G's integrated graphics are DirectX 9- and OpenGL 1.4-compatible, support QXGA (2,048-by-1,536 pixel) resolution at 85Hz and include hardware-accelerated pixel shading, shadow maps, volumetrix textures, depth bias and two-sided stencils. Intel says that the 915G delivers around 1.7 times better 3DMark 2001 performance than the graphics subsystem on the previous 865G chipset.
High Definition Audio
The High Definition Audio on the chips runs at a maximum of 192KHz 24-bit sample rate with eight channels, plus Dolby, DTS and DVD-Audio support. It also supports array microphones with up to 16 elements, a rather under-utilised technology that's useful for noise-cancelling voice recognition systems. This may be a feature of future operating systems. The final trick that the audio subsystem knows is 'jack retasking': it senses whether you've plugged a microphone, speaker or line-level audio connection into each jack and routes the audio signal appropriately. This could spell the end of the incomprehensible audio icon.
Intel's High Definition Audio supports array microphones with up to 16 elements -- useful for voice recognition systems.
Get on the bus
Today's venerable PCI standard allows data to travel at up to 133MB/sec. in one direction only; stuff headed the other way has to wait its turn. A standard PCI Express bus (called an X1) will offer transfers of up to 250MB/sec. in each direction, for a total of 500MB/sec. This should help speed up basic PC operations -- and it'll vastly improve gigabit networking, which runs into serious bottlenecks on the PCI bus.
Another area that's always in need of more bandwidth is graphics. Years ago, to support the evolution of powerful graphics cards, the PC industry abandoned the PCI bus and created the Accelerated Graphics Port (AGP). PCI Express brings graphics back into the fold and offers 4GB/sec. concurrent transfers to and from PCI Express-based graphics cards. In comparison, today's 8x AGP bus offers 2GB/sec. of shared bandwidth. Intel's 925X Express and 915P Express chip sets will offer a PCI Express graphics port, but no AGP. The 915G Express will include Intel's new integrated Graphics Media Accelerator 900.