Intel 945 Chipset

The new Centrino Duo platform includes a new chipset, too. It’s not surprising since Core Duo processors use a 667MHz system bus that is not supported by Intel’s last-generation i915PM/GM chipsets. The new chipset for the Core Duo processor is called i945PM/GM (Calistoga) which resembles the name of a similar product for desktop computers. Well, the new mobile chipsets are really developed out of their desktop analogs with power-saving options in mind. The i945PM/GM can control their own power consumption as well as optimize the consumption of the memory modules installed in the system.

The i945PM/GM do not differ much from Intel’s earlier mobile chipsets (i915PM/GM), at least, there is nothing completely new in them. They have just improved over the older ones in some characteristics. The improvements are not to be underestimated, though.

Besides the faster Quad Pumped Bus (which works now at 667MHz and yields a bandwidth of 5.3GB/s), the i945PM/GM chipsets support faster DDR2 SO-DIMMs. The earlier mobile chipsets could only work with dual-channel DDR2-533 SDRAM, but the new ones support dual-channel DDR2-667 SDRAM. It means the memory subsystem bandwidth has increased to 10.7GB/s, which should have a positive effect on the performance of mobile computers.

The Intel 945 mobile chipset family consists of two products: an i945GM with an integrated graphics core and a discrete i945PM. The increased memory bandwidth we’ve talked about above may improve the performance of systems that use some of the system RAM for the purposes of the graphics subsystem. We mean i945GM-based platforms in the first place.

The graphics core in the i945GM is somewhat different from the one in the last-generation i915GM chipset and is indicated by the different name, Intel Graphics Media Accelerator 950 (the older was called GMA 900). You shouldn’t look for any dramatic changes in the new graphics core, though. Its architecture has remained the same. GMA 950 has 4 pixel pipelines and is capable of mapping up to 4 textures per clock cycle. Like GMA 900, it provides hardware support for Pixel Shader 2.0 and software support for Vertex Shader 3.0 and T&L. GMA 950, and GMA 900 too, is a fully DirectX 9 compatible graphics accelerator.

You may wondering what is the difference between the new and older graphics cores, but the answer is simple – frequency. Besides the higher system memory frequency (which is also used as graphics memory), the graphics core frequency has been raised, too. The GMA 900 core worked at 333MHz at the maximum (the frequency could be lowered to save power), while GMA 950 can be clocked at 400MHz.

Like the i945PM, the i945GM is equipped with a PCI Express x16 bus for connecting an external graphics card – the new chipsets do not differ from their predecessors in this respect. The i945PM/GM use an ICH7-M chip as a South Bridge; it is connected to the North Bridge via a special-purpose Direct Media Interface (DMI) with a peak bandwidth of 2GB/s.

The South Bridge in the i945PM/GM chipsets supports one Parallel ATA and two Serial ATA ports, eight USB 2.0 ports and integrated High-Definition Audio. It also supports six PCI Express x1 lanes for peripheral devices like a Gigabit Ethernet controller or Wi-Fi adapter.

To finish this section of the article we offer you a table in which the i945PM/GM chipsets are compared with the chipsets from the last-generation Centrino platform: