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Intel's 915G and 925X Express chipsets


Intel remakes the PC platform
— 1:35 AM on June 21, 2004

YOU MAY BE aware that Intel is introducing a new PC expansion spec called PCI Express, designed to replace the not-so-gracefully-aging PCI bus and its prodigal son, AGP. This move has been planned for some time now and needed for even longer. PCI is older than the hills and slower than Jessica Simpson counting her change. What you may not know is that Intel was not content just to replace the PCI bus. Instead, the company has undertaken to freshen up nearly the entire PC platform, with new specifications for everything from memory to storage, graphics, power, enclosures, cooling, processor sockets, and audio.

The intent of these wide, sweeping changes is clear: to inflict as much pain on the industry as possible in the shortest time window.

Err, sorry.

What I meant to say was that Intel clearly intends to clean up the last vestiges of the circa-1990s PC platform at once, weeding out weaknesses and pulling open bottlenecks. The marketing spin on all of this says it's about enhancing the user experience and making the PC a better citizen in the "digital home," where networked PCs replace VCRs and other such media devices. For once, I'm somewhat persuaded by the spin, because many of these changes should make computing smoother and easier, better suited to the playback of high-definition audio and video. However, this major overhaul of the PC isn't just about making a better TiVo replacement. There's much more to it than that.

We've tested the whole shebang, from the Intel 915 and 925X Express chipsets to new processors including the Pentium 4 model 560 at 3.6GHz. We've tested PCI Express graphics cards from ATI and NVIDIA, and we've benchmarked Maxtor's impressive new MaXLine III Serial ATA hard drives with support for Native Command Queuing. Read on to learn more about what each of these changes means for you and to see how this first wave of next-generation PC hardware performs.

The heart of the matter
At the heart of Intel's PC overhaul is that too-often overlooked component, the core logic chipset. These two chips act as the traffic cop inside a personal computer, allowing all the devices to communicate and function together. Most of the major features you see on a checklist from Dell or HP are conferred by a system's chipset, as well. Today, Intel is introducing a lineup of three new 900-series Express chipsets, the 925X, 915P, and 915G. I'll give you a brief overview of this lineup's new features, and then we'll look at the new stuff in more depth. If you're confused by some of the terminology, hang on, because we'll be explaining much of it on the following pages.


A block diagram of the 925X Express chipset. Source: Intel.

The three 900-series chipsets have a lot in common, as one might expect. Their north bridge chips—or memory controller hubs (MCH), as Intel likes to call them—include a PCI Express X16 interface for graphics, replacing AGP, and a new memory controller capable of working with DDR2 memory.

As in the past, Intel has enabled and disabled features on its MCH chips to create three distinct products. The 925X is the high-end chip; it will have faster internal timings in its memory controller and support for ECC memory to enhance data integrity for workstations. The 915P is Intel's mainstream chip; unlike the 925X, it retains support for DDR memory. And the 915G is essentially the 915P plus built-in graphics.

All three of these north bridge chips talk to the other chip in the set, the south bridge—or I/O Controller Hub (ICH) in Intel-speak—via a new, PCI Express-like link, dubbed DMI, that has a data rate of 1GB/s in each direction for a total of 2GB/s. Until now, Intel's chipsets had been saddled with Intel's Accelerated Hub interconnect running at 266MB/s, so this change is welcome.

The change is also necessary, because the I/O-oriented south bridge will now be doing lots more input and output. There are four flavors of the new ICH6 chip, and all them share some common features, including four Serial ATA 150 ports, one ATA/100 port, eight USB 2.0 ports, Gigabit Ethernet, support for Intel's new High Definition Audio, and four lanes of PCI Express expansion capacity. That features list represents an upgrade in almost every category save one: it's down one ATA/100 port. Intel's obviously ready to move the market away from ATA hard drives. Still, the ICH6 series retains support for all sorts of legacy I/O standards, including up to six PCI slots, just in case you're a glutton for punishment.

As in the past, the ICH models with support for disk arrays, or RAID, get an "R" at the end of their names. Also, some models of the ICH will now come with 802.11g wireless networking capability. Those models will get a W attached to their names. So at the end of the day, you have four variants of the new ICH: the vanilla ICH6, ICH6R, ICH6W, and the super-deluxe ICH6RW. Make mine an RW, please.

That's the 10,000-foot overview of the 915 and 925X Express series chipsets that bring all these new features to the PC for the first time. Now let's talk about some of the important features in more detail.