Difference between Pro Tools PCI-X HD cards.

[MacOS Plus]

  For future reference, should I ever get some of these, I'm wondering about a minor difference I noticed in photographs of Pro Tools PCI-X HD cards (not PCI Express).  I know the rough basics of the Core, Accel and Process variants, but I was wondering about the difference between cards having one or two DIN connectors on the back.  Is the only difference the number of available ports?  Are the ones with only a single port newer revisions?  Do all revisions of a particular card type contain the same number of DSP chips?