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The overview for the 5500 and 5520 chipsets state that there is a total bandwidth of up to 48GB/s on each PCI Express x8 interface.

http://www.intel.com/products/server/chipsets/5500-5520/5500-5520-overview.htm

My understanding (admittedly from wikipedia) is that PCI-e Gen 2 runs at 500MB/s per lane. The 5520 has 36 lanes, and so would be limited to a total of 18GB/s.

Am I missing something here, or is Intel's claimed 48GB/s a typo that should say 18GB/s ?

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2 Answers 2

up vote 0 down vote accepted

Certainly a typo. The datasheet says that you have 2 8GB/s 16x ports and 1 4x port.

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I glad about that. Thanks. –  Martin Mar 15 '10 at 12:08

To add to wazoox's post you are correct but I can see how they've got confused. The lowest-end-part, the 5500, has 24 x PCIe 1.1 channels, each at 2 giga-BIT/s, it's like a lowest-common denominator basically, i.e. they can both do 48 giga-BIT/s (or more of course) - someone's just used the wrong 'B'/'b' - happens all the time :)

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Indeed. Some of the PCI-express docs talk in terms of giga-transfers (GT/s) just to add to the fun. My original problem was to find out the difference in PCI-express performance between HP DL360-G5 and G6: the HP documentation was so vague that I had to chase back to the docs for chipsets - which just confused me more. I have reported the typo to Intel: it will be interesting to see if they fix it. –  Martin Mar 16 '10 at 15:26
    
Ah, wish you'd said, I'm a HP specs guy, the G5 uses 5000P not the 5500 by the way, either way both the 5000P and the 5520 box have 24 lanes but the G6 supports 'Gen 2' adapters therefore exactly doubling bandwidth - hopefully this answers your question. –  Chopper3 Mar 16 '10 at 22:14

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