The Core Logic
The platform shift brings with it a clutch of new supporting core logic. The enthusiast gets catered for with a two chipset split, analogous to the Canterwood/Springdale split at the upper end of the Socket 478 chipset range. Both are paired with the ICH6-series of southbridge I/O chips.Intel i925X - Alderwood
Alderwood is the top performer from the new enthusiast chipset pair. It supports only DDR-II memory (two channels with ECC support), only 800MHz LGA775 processors and PCI Express 16X for its graphics interconnect (rumours abound of a dormant AGP interface though). It uses a 2GB/s DMI link to the southbridge, doubling the previous link bandwidth available on any Intel core logic.In terms of raw numbers, the PCI Express 16X link is 8GB/s full duplex, 4GB/sec in each direction. In comparison, AGP8X is a 2GB/sec upstream connection, from host to GPU (for data upload) but only a ~500MB downstream connection for GPU to host writebacks.
The memory controller houses a pair of DDR-II channels, capable of 533MHz maximum speed giving an 8.5GB/sec (533MHz, two 8-byte busses) peak theoretical figure. The memory controller is also capable of running in a more flexible set of configurations, compared to Canterwood or Springdale. For example, you can populate one memory controller with a pair of 256MB DIMMs and put a 512MB DIMM in a slot that's connected to the second controller, and get full dual-channel operation. As long as the connected memory total for each bank is the same, the chipset runs in interleaved dual-channel mode.
The CPU bus remains identical to the outgoing core logic, at least for the time being. An 8-byte bus at 800MHz, the peak figure of 6.4GB/sec remains.
The mismatch in CPU to memory controller bandwidth crucially sits in favour of the memory, at 533MHz, with a perfect match at 400MHz. With excess bandwidth more desirable than a deficit, the design sits well from a theoretical point of view. In practice, the bandwidth figures obtainable will be much lower, but we'll investigate that later.
With Alderwood employing PAT-like memory bandwidth and access enhancements, that feature is what differentiates it from Grantsdale in terms of performance. Features differentiate it otherwise.
Intel i915P - Grantsdale
Grantsdale differs only from Alderwood in that it will run future 533MHz bus LGA775 processors, as well as the 800MHz versions, and that it also supports regular DDR-I SDRAM, in addition to supporting DDR-II. Early boards spotted in the wild are supporting either standard, depending on configuration.It supports the same PCI Express 16X link for graphics and the same 2GB/sec link to the ICH6-series of bridges.
ICH6-series bridge
The ICH6 is possibly the most exciting part of the new core logic. It can drive up to eight USB2.0 ports, integrates a next-generation 6-port (4 native, 2 with an extra PHY) SATA controller with NCQ (native command queuing) and flexible RAID, adds Intel's new High Definition Audio link for supporting CODECs, implements four PCI Express 1X peripheral interfaces and the usual 6-port PCI controller and other sundry I/O interfaces such as legacy serial and parallel.It also includes a WiFi MAC and PHY in the 'W' version of the bridge, for integrated wireless networking. It's an 802.11g implementation which means 54Mbit/sec peak transfer speed. It is also soft-configurable as a wireless access point.
Let's cover the ICH6 features in turn, bar the WiFi.
