Dan,
Thank you once again for your help and insights. It is such a benefit to have your input. The OP wanted to add in a HP USB3.0 card, which was released by HP for the Z600 era workstations as an option, and also use a front panel from a Z620 fed USB3 from that card because it would be a clean install and a great look. Those Z600 option cards from HP had 2 forms.... the rare early card was made by NEC/Renasus, and the later common version of the card was made with a TI chip. It was the winner because it upped the USB3 ports from 2 total (on the card's backplane) to 4 total (2 on the backplane, and two more via a standard 2x10 USB3 "motherboard type header" for running a USB3 dual cable set to out front. HP called that their "2x2" card, and later used the Texas Instrument chip on the motherboard of the Z620 era workstations. That is why there are TI USB drivers included for the Z620, to run its on-board TI chip.
Having said that, from your insights, the powered redrivers in the Z620's small black box probably receive +5VDC supply and ground for each of its 2 USB3 ports built in up front.... hence two total orange power feeds and two total black ground, I'm guessing. Those 4 wires come into the little black box via the thinnest black cable going forward into that box.
What I have done with my xw6600 work is to put in that same TI based 2x2 HP card running it in my lower PCIe x16 video slot (which is PCIe Generation II, as is the top video port). That way I can get the bandwidth needed to/from the PCIe bus to match USB3 capabilities. That has worked very reliably, and I have used high quality USB3 thumbdrives from Sandisk to do speed testing to prove I'm getting USB3 speeds. Key point.... I believe HP engineered the redrivers you described into that 2x2 USB3 option card, because it works just fine over those longer cables you see in my post above. Quite a few USB3 cards on the market now have that type of 2x10 header (1 row actually is 9, with a key hole epoxied in).
So, for the OP the use of the front panel from a Z620 in a Z600, even if it fits, adds in the complexity that his redrivers in that small black box won't be powered correctly because the Z600 does not have the power feeds/grounds off of the motherboard like the Z620 does. He might be able to hack those in from power supply feeds from above, but who knows what risks that entails? If he chooses to do that then I'd sure recommending carefully confirming that orange is positive and black is ground.
Hence, maybe my off hand suggestion that he use the HP 2x2 card and the Akasa front USB3 interface shown in the pic above might suffice better.... it sure has been working very well in my xw6600 builds.
For completeness.... the rest of the PCIe slots in the xw6600 are PCIe Gen I, and all the PCIe slots in a xw6400 are PCIe Gen I. That is why I've only done this mod on the xw6600s here.
Always good to get your input......... and thanks again.
