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Actually, yeah. PowerMac7,3 can either denote June 2004 or early 2005 models. It either has 3x PCI-X (June 2004) or 3x PCI (Early 2005).
 
There were several models made, so it can be confusing, but use the Apple Menu-About this Mac-More info System Profiler to check how many RAM slots and the video card your machine has, than download Mactracker from www.mactracker.ca compare the info obtained above with the info from Mactracker. That should tell you which machine you have and the PCI slot information is listed also.:)
I have one of the Late 2005 models 2.0GHz and it has PCI-e slots, the only models that had those were the last ones produced in October of 2005. Earlier models had PCi first and then PCI-X, in order. Do you have the user manual for your machine? That info should be documented there too.
 
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