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About COM Express

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  • About COM Express

    Hi everyone,

    It is not so easy to understand the differences between Type 2, Type 6 …
    As far I understand, new release of COM Express is 3.0 and involves Type 7.

    I would like to develop a carrier board allowing external GPU board.
    I downloaded the COM Express Carrier Board Design Guide on It is bases on release 2.0.
    The question is: should I use Type 2 or Type 6?
    In the documentation, they speak about a signal on pin D97 (Type 6) named "PEG_ENABLE#".
    Why don't we find such signal on Type6?
    The Purpose of this signal is to tell that we use internal GPU or not.

    Thanks a lot.

  • #2
    I do not remember exactly, but you may need to choose based on peripherals you need (2 looks like an old one, 6 looks more suitable for today's boards) and on the module you would like to use. This is what I found (simple comparison) - is this what you mean?


    • #3
      That's a good start for an answer. Peripherals are standard. What I do not understand is that signal
      on Type 2 that is not present on Type 6.


      • #4
        For MXM board, you'll use PEG Signals (16 lines).
        The other PCIE lines will be used for SSD and wireless board.


        • #5
          When I was not sure how to connect some signals, I always had a look at schematic of the other baseboards which were supported by that specific module.

          PS: I do not know why the signal is not on both, probably it was not needed (?) e.g. card can be enabled in BIOS or by some other different ways (just guessing)