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The P35 Express chipset
Intel is set to release a whole line of new "3 series" chipsets, from low-end models with integrated graphics to a high-end X38 Express that's set to replace the aging 975X in the third quarter of this year. The P35 Express sits in the middle of this new core logic range, replacing the P965.


Source: Intel

Busting out a block diagram of the P35 Express reveals relatively few surprises. Most of the action is at the north bridge, where the P35 offers native support for front-side bus speeds up to 1333MHz. Nvidia's latest nForce 680i SLI (and that company's more budget-oriented 650i SLI) also support 1333MHz front-side bus speeds, but as you can see in the north bridge feature comparison chart below, Intel's P965 and 975X do not.

P35 Express P965 Express 975X Express nForce 680i SLI SPP
Front-side bus 1333/1066/800MHz 1066/800MHz 1066/800MHz 1333/1066/800MHz
Memory controller DDR2-800/DDR3-1066 DDR2-800 DDR2-667 DDR2-800
PCI Express lanes 16 16 16 18
Multi-GPU support CrossFire* CrossFire* CrossFire SLI
Chipset interconnect DMI DMI DMI HyperTransport
Peak interconnect bandwidth 2GB/s 2GB/s 2GB/s 8GB/s

Along with the P35's support for a 1333MHz front-side bus comes compatibility with 45nm Penryn processors that are expected to make their debut in the second half of the year.

Things get a little more interesting when we look at the memory controller, where the P35 stands out as the only core logic chipset to support dual channels of DDR3 memory. Intel has only validated DDR3 speeds up to 1066MHz, but as we've seen with previous chipsets, motherboard makers are free to offer the necessary dividers to run memory at higher speeds. The Asus motherboard we'll be looking at today, for example, supports DDR3 speeds up to 1333MHz, albeit only in tandem with a 1333MHz front-side bus.

If you're not keen on upgrading to DDR3, the P35 Express also has a dual-channel DDR2 memory controller that's been validated up to DDR2-800. Again, motherboard makers are free to support faster memory bus speeds. They're even free to create motherboards with both DDR2 and DDR3 memory slots, although this is another solution Intel hasn't officially condoned. Intel does concede it's possible, though, just as long as you don't try to run DDR2 and DDR3 at the same time.

We've actually seen Intel-based motherboards supporting dual memory types before. Those boards were based on the 915 Express chipset, which featured DDR and DDR2 memory compatibility just as the latter was debuting in the market.

Apart from the memory controller and front-side bus, the P35 Express looks a lot like the P965. You still get 16 lanes of PCI Express at the north bridge, but those lanes can't be split up between a pair of graphics cards for CrossFire. Instead, the P35 supports multi-GPU configurations much like its predecessor did: primary graphics cards get 16 lanes of PCIe bandwidth from the north bridge, while secondary cards hang off a four-lane connection from the south bridge. This configuration puts additional stress on the 2GB/s DMI interconnect that runs between the chipset's north and south bridge components, but as we saw with the P965 Express, that doesn't seem to slow CrossFire performance.

We should note that although there's been some talk of Bearlake's support for second generation PCI Express, that's only for the high-end X38 Express that's scheduled for release later this year. The P35's PCI Express lanes are all first-generation PCIe.

ICH9R ICH8R ICH7R nForce 680i SLI MCP
PCI Express lanes 6 6 6 28
Serial ATA ports 6 6 4 6
Peak SATA data rate 300MB/s 300MB/s 300MB/s 300MB/s
AHCI Y Y Y N
Native Command Queuing Y Y Y Y
RAID 0/1 Y Y Y Y
RAID 0+1/10 Y Y Y Y
RAID 5 Y Y Y Y
Matrix RAID Y Y Y N
ATA channels 0 0 1 1
Max audio channels 8 8 8 10
Audio standard HDA HDA HDA HDA
Ethernet 10/100/1000 N N 2 x 10/100/1000
USB ports 12 10 8 10

At the south bridge, the ICH9R chip that will most commonly be paired with the P35 on enthusiast motherboards might as well be called the ICH8R Plus. This is essentially last year's south bridge with a little extra kit, including two additional USB ports and a Gigabit Ethernet MAC.

The GigE MAC is the most notable new addition, and it's one we're happy to see. Gigabit Ethernet has become ubiquitous on even budget motherboards, and that functionality might as well be integrated into the chipset rather than farmed out to an auxiliary chip. Curiously, though, all three of the P35 Express-based motherboards that have arrived in our labs thus far feature third-party Gigabit Ethernet controllers. There may be a GigE MAC aboard the ICH9R, but mobo makers don't appear to be taking advantage of it yet.

It's a shame that more motherboard makers aren't using the ICH9R's integrated networking capabilities, because that's really the only new feature. The chip sports six 300MB/s Serial ATA RAID ports just like its predecessor, the ICH8R, and it's still missing an IDE port. At least by now there are enough affordable SATA optical drives on the market to make the lack of IDE support easy to swallow. Motherboard makers will probably continue to offer IDE ports through third-party storage controllers, as well.

Perhaps the most surprising attribute of the ICH9R is the fact that the chip's being fabbed using relatively pedestrian 130nm process technology. With Intel apparently mastering 65nm production for its Core 2 line and already pushing 45nm for Penryn, we'd expected a process shrink for newer chipsets. The P35 north bridge is built on a 90nm process, at least.

Asus' P5K Deluxe and P5K3 Deluxe motherboards
We've been testing the P35 Express in our labs for the past week on P5K3 Deluxe and P5K Deluxe motherboards courtesy of Asus. The former takes advantage of the P35's support for DDR3 memory while the latter uses plain old DDR2.


Asus' P5K3 Deluxe motherboard

Apart from differing on the memory front, the P5K3 and P5K Deluxe are virtually identical. Both are loaded with intricate heatpipe chipset cooling, eSATA, Firewire, and integrated Wi-Fi capabilities. We'll be taking a closer look at these boards as well as others based on the P35 chipset in the coming weeks. Stay tuned.