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Intel's P45 Express chipset

Die-shrinking the dynasty

Intel's P35 Express chipset has been a revelation for the Core 2 platform, delivering the same excellent performance, low power consumption, and generous overclocking headroom of more expensive X38 and X48 variants at a much lower cost. Or at only a slightly lower cost, depending on whether you prefer your motherboard loaded with more frills and extras than the spawn of Pimp My Ride. But that's the beauty of the P35; it's equally capable of powering mainstream desktops, high-end gaming rigs, and the sort of balanced best-bang-for-your-buck systems that enthusiasts tend to build.

If you've been around for long enough, the P35's success should come as no surprise. Intel's mid-range chipsets have been consistently solid year after year, establishing a virtual dynasty in an industry that doesn't always look kindly upon incumbents. It's no wonder, then, that expectations are high for the P35's successor, the new P45 Express.

Intel hasn't messed with the formula much for the P45, but there are a few new tricks up its sleeve. A redesigned memory controller promises to take better advantage of processors with 1333MHz front-side bus speeds, for example. Second generation PCI Express connectivity has also been added to the mix along with a more balanced approach to CrossFire configurations. And ever the efficient manufacturer, Intel has managed to shrink the whole thing down on a 65nm fabrication process.

The motherboard market is about to be saturated with a tidal wave of new designs based on the P45 Express, each with its own set of unique features and capabilities. We've already taken an early first look at what Asus is bringing to the table. Now that Intel has made the P45 official, we're diving a little deeper, this time with a couple of new motherboards from Gigabyte. Read on for a in-depth look at how the P45 Express fares against a collection of DDR2- and DDR3-equipped competitors ranging from its popular predecessor to Nvidia's uber-high-end nForce 790i SLI Ultra.

A die-shrunk refresh
Intel employs a "tick-tock" cadence for processor development, rolling out new architectures on each tock and then shrinking them with more advanced process technologies with each tick. Judging by the all around awesomeness of the recent "Penryn" 45nm die shrink of the original Core 2 microarchitecture, the tick-tock strategy appears to be working well. So well, in fact, that I think it may have been applied to the P45 Express, which in many ways looks like a die-shrunk P35.

Like Penryn, the P45 packs a few new elements alongside its move to a finer fabrication process. The most notable among these is easily the inclusion of second generation PCI Express connectivity. 16 lanes of PCIe 2.0 are available in the P45's north bridge chip, and they can be configured as either a single x16 link or as a pair of x8s for CrossFire. With multi-GPU configurations finally offering compelling performance at affordable prices, the P45's balanced approach to CrossFire is much appreciated. The P35 chipset wasn't capable of splitting its north bridge PCI Express lanes, forcing secondary graphics cards to hang off just four south bridge PCIe lanes and compete for limited interconnect bandwidth.

In addition to refreshing the P45's PCI Express component, Intel redesigned the chip's memory controller to better exploit the 1333MHz front-side bus speeds made common by the Penryn Core 2 refresh. The memory controller is still compatible with both DDR2 and DDR3 memory, and it now supports up to 16GB of the former. You'll only be able to pair up to 8GB of DDR3 memory with the P45, which given current market prices, may be a blessing in disguise.

X48 Express X38 Express P45 Express P35 Express nForce 790i SLI Ultra SPP nForce 780i SLI SPP
Front-side bus 1600/1333/1066MHz 1333/1066MHz 1333/1066MHz 1333/1066MHz 1600/1333/1066MHz 1333/1066MHz
Memory controller DDR2-800
DDR3-2000* DDR2-800
PCI Express 1.1 lanes 0 0 0 16 2 0
PCI Express 2.0 lanes 32 32 16 0 32 32
Multi-GPU support CrossFire CrossFire CrossFire CrossFire* SLI SLI
Chipset interconnect DMI DMI DMI DMI HyperTransport HyperTransport
Peak interconnect bandwidth 2GB/s 2GB/s 2GB/s 2GB/s 8GB/s 8GB/s

Like the P35 that came before it, the P45 only officially supports DDR2 memory speeds up to 800MHz. DDR3 memory speeds top out at a more generous 1333MHz. However, it's worth noting that motherboard makers are largely ignoring Intel's official specifications and loading BIOSes with the memory bus multipliers necessary to hit higher speeds.

Mobo makers are also advertising P45 boards capable of hitting 1600MHz (quad-pumped) front-side bus speeds despite the fact that Intel only endorses FSB speeds up to 1333MHz. Intel appears content to limit official support for the 1600MHz front-side bus required by its obscenely expensive Core 2 Quad QX9770 flagship to the high-end X48 chipset, which also doubles up on the P45's PCI Express lanes.

With even the high-end X48 relying on Intel's DMI chipset interconnect, it's no surprise that the P45 uses the same link to tie together its north and south bridge components. DMI has been around for a while now, and its 2GB/s of bandwidth looks a little light next to the speedy 8GB/s HyperTransport interconnect used in nForce chipsets for Core 2 processors. Keep in mind, though, that Nvidia needs the extra bandwidth because it's made a habit of hanging graphics cards off the south bridge.

ICH10R ICH9R nForce 790i SLI MCP nForce 780i SLI MCP
PCI Express 1.1 lanes 6 6 28 28
Serial ATA ports 6 6 6 6
Peak SATA data rate 300MB/s 300MB/s 300MB/s 300MB/s
Native Command Queuing Y Y Y Y
RAID 0/1 Y Y Y Y
RAID 0+1/10 Y Y Y Y
Matrix RAID Y Y N N
ATA channels 0 0 1 1
Max audio channels 8 8 8 8
Audio standard HDA HDA HDA HDA
Ethernet 10/100/1000 10/100/1000 2 x 10/100/1000 2 x 10/100/1000
USB ports 12 12 10 10

While the P45's north bridge component at least has some new hotness to brag about, the chipset's ICH10R south bridge chip looks like little more than a die-shrunk ICH9R. The ICH9R certainly wasn't hurting for an upgrade, though; six Serial ATA RAID ports remains the standard and Intel's ability to mix and match array types with "Matrix" RAID configurations is still unique among even high-end chipsets.

Heck, we're even over Intel's decision to exclude an IDE port from its recent chipsets, in part because Vista plays well with the JMicron storage controllers most motherboard makers have been forced to use to provide "parallel" ATA support. And offering 12 USB ports still keeps the ICH10R up with the Jonses, even if it looks like those ports are the same ones you'll find in the old ICH9R.

Like the ICH9 family, the ICH10s also feature a Gigabit Ethernet MAC. We didn't see many manufacturers take advantage of this capability in the ICH9R, ostensibly because Intel didn't have a necessary PHY physical interface chip ready at launch. The ICH9R's integrated networking capabilities finally got a chance to strut their stuff on Intel's DX48BT2 "Bearlake 2" motherboard, which offered great throughput and the lowest CPU utilization we've seen from any chipset-level GigE implementation. We can only hope more motherboard makers take advantage of the ICH910R's Gigabit credentials this time around.

About the only thing really missing from the ICH10R is PCI Express 2.0 connectivity. The onboard peripherals and x1 slots normally serviced by south bridge PCIe lanes aren't exactly begging for bandwidth these days, but it wouldn't hurt to have generational parity between PCI Express implementations in the P45's north and south bridge components.