P55 Chipset Overview



We have just one chipset now as typical Northbridge functions are moved onto the Lynnfield processor. Just like its Bloomfield-based Core i7 big brother, Lynnfield based CPUs have integrated memory controllers. The DDR3 memory channels are dual channel unlike the triple channel setup on Bloomfield. Lynnfield currently supports 16GB of memory, solidly placing it in the midrange category. However, official memory speeds now reach 1333MHz instead of 1066MHz on Bloomfield. The biggest difference between the two processer families is that Lynnfield stuffs 16 lanes of PCI Express 2.0 connectivity into the processor, thus alleviating the need for a Northbridge.

Those 16 PCIe 2.0 lanes can be configured as a single x16 link or split between a pair of x8s for multi-GPU configurations with a set of PCIe switches. CrossFireX support is a given but SLI support depends upon the motherboard manufacturer providing the right amount of funds to Nvidia for certification. For those unwilling to just accept 16 PCIe 2.0 lanes, EVGA already has a P55 board featuring the nForce 200 bridge chip with full support for three-way SLI.

What was known as the Integrated Controller Hub (ICH) on previous chipsets (such as the ICH10R) is now referred to as the P55 Express Platform Controller Hub, or PCH. The chip is based on 65-nm process technology. As such, it is a lot smaller than the ICH10 series with a total die area of around 76.5 mm².

  AMD SB750 Intel ICH10R Intel P55
Additional PCI Express None 6 x1 PCIe 1.1 8 x 1 PCIe 2.0
USB 12 ports 12 ports 14 ports
SATA (300MB/s) 6 ports 6 ports 6 ports
PATA 2 channels None None
RAID* RAID 0/1/5/10 RAID 0/1/5/10 RAID 0/1/5/10
HD Audio Interface Yes Yes Yes
Ethernet Not Integrated Intel Gigabit LAN Intel Gigabit LAN
Northbridge Interface 4 lane PCIe 1.1 DMI 1Gb/s each direction, full duplex DMI 1Gb/s each direction, full duplex

The P55 Express PCH provides six 3 Gb/s SATA ports, 14 USB 2.0 ports, a Gigabit Ethernet MAC , HD Audio interface, and eight lanes of PCI Express 2.0 goodness all for about $40. That price tag buys you two additional USB ports and two additional PCIe lanes over the $3 ICH10R. One other change worth mentioning is that the Gigbit Ethernet MAC will use one of those PCIe lanes if enabled.

The PCI Express lanes are version 2.0 but Intel decided to limit their speed to PCIe 1.x specs at 2.5GT/s. Why? We believe with the DMI link continuing to operate at 1GB/s in each direction, a decent 6Gb/s SAS/SATA RAID card and a few upcoming 6Gb/s drives could easily saturate the link. The P55 Express PCH consumes a little over 4.5W during normal operation. Considering the specifications on AMD’s upcoming SB8xxx chipsets, it appears we have a PCH Gap brewing.

Index Gigabyte GA-P55M-UD2 Features
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  • MadMan007 - Monday, October 05, 2009 - link

    To follow up on this, the comment was based on the first few paragraphs. I looked over Intel's manual for their 'extreme' mATX board for my post about it and Intel actually states their mobo has PCIe 2.0 lanes to the additional PCIe slots. Not surprising for the 8x slot I guess but it is for the 1x slots and it seems unlikely Intel would misquote specs.

    On a related note there is one thing I've not seen yet from any review and that is how PCIe lanes get assigned, mainly to the primary 16x slot, when populating a secondary PCIe slot with a 1x or 4x card. Do the lane splitter chips assign 8x lanes to a secondary slot which has a 1x or 4x card or what? Not a huge deal but it's a little thing that would be nice to know.
    Reply
  • Gary Key - Monday, October 05, 2009 - link

    The PCIe lanes coming off the P55 are 2.0, the problem is that they are running at 1.x speeds (2.5GT/s). On these two boards, the x16 slot is off Lynnfield and will not be affected by any card placed in the x4 or x1 slots off the P55. Reply
  • Mr Perfect - Tuesday, October 06, 2009 - link

    I should probably know this, but what does a 2.0 slot running at 1.x speed bring to the table that a 1.x slot doesn't? Does it provide more power or something? Reply
  • MadMan007 - Tuesday, October 06, 2009 - link

    Yes I was half right with my post and nothing Gary said was technically wrong it's just misleading. They are PCIe 2.0 spec slots but running at half speed, this is clear from Intel's chipset disgram. It's really a farce to call them PCIe 2.0 though because the overridingly most important change from 1.x to 2.0 is the double bandwidth, there are other changes like the power rating I believe and maybe some low level changes but nothing major. I think it's false advertising to call them PCIe 2.0 personally because they don't fully conform to the spec.

    In any case I'd still like to know how many lanes the main CPU-based slot retains when a 1x or 4x card is placed in a secondary CPU-based PCIe slot. Anandtech seems to be more receptive to odd little investigations like this so I hope Gary will check it out.
    Reply
  • james.taylor - Monday, May 10, 2010 - link

    Hi Gary, Thank you so much for this information Reply
  • james.taylor - Monday, May 10, 2010 - link

    again thanks but if you want to buy new memory then http://www.memoryx.net/ this can help you Reply

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