I have a number of awkwardly shaped connectors that I need to cram into a single PCI Express slot metal bracket without any of them colliding with the host PC case's metalwork. The connectors are a mixture of proprietary and standard.

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My connectors will obviously need to be arranged so that they do not interfere with the PC case's metalwork so this means they they must fit within some sub-set area of the metal bracket (the red box).

Where can I find the official dimensions of the red box? (specifically the maximal area that I'm allowed to use while still being "compliant" with the physical spec of PCIe).

The specs that I have seen give details on the spatial relationship between the metal bracket and the add-in card PCB, but they do not seem to give details of the space that may be used for connectors to pass through.

PC cases vary so much from one brand to another (high-end versus low-end particularly) that I'm worried that if I don't get this right early on in the design then I'll have to re-spin all my PCBs and metalwork later on when someone finds a case that this device won't fit into.

  • \$\begingroup\$ Best thing to do is look up the ATX specification. \$\endgroup\$ Commented Feb 1, 2018 at 19:47
  • \$\begingroup\$ it is probably a PC case spec, not a PCI spec \$\endgroup\$
    – jsotola
    Commented Feb 1, 2018 at 19:48
  • \$\begingroup\$ Put it in the middle. \$\endgroup\$ Commented Feb 1, 2018 at 19:54
  • \$\begingroup\$ I was wrong, its the PCIe CEM spec that you want (card electromechanical spec). \$\endgroup\$ Commented Feb 1, 2018 at 20:03
  • \$\begingroup\$ @MarkoBuršič, as a precaution I'm shipping a crowbar with each unit. :) \$\endgroup\$
    – user98663
    Commented Feb 1, 2018 at 20:18

1 Answer 1


According to the PCIe Card Electromechanical Specifications (CEM), we have the following specification for connector openings:

CEM Spec Connector Openings

Image Source - CEM Spec rev 1.1, Section 6, Figure 6-2, page 73

So your magic numbers are 89.9mm x 12.06mm.

That diagram also shows you how the space positions relative to the PCB.

If you follow that spec and it doesn't fit into a given case, it is not your problem as you've conformed to the specification that the case designer should also have conformed to.

  • \$\begingroup\$ That looks like what I need. I'll try to cross reference this with our own in-house documentation (which is probably out-dated to be honest, might need to renew some licence$!). Based on this info I'm going to have to lose one connector entirely, but it's still do-able. Thanks for the help, Tom. \$\endgroup\$
    – user98663
    Commented Feb 1, 2018 at 20:28
  • \$\begingroup\$ @Wossname a common approach is to combine several connectors into a single one (or use a smaller connector) and use a cable adapter to break them out. For example if you needed several BNCs, you could use a smaller SMA connector then adapter cable. \$\endgroup\$ Commented Feb 1, 2018 at 22:27

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