Powering Stratix IV Dev kit via HSMC

The rails you refer to on the HSMC connector are, typically, there to provide power to any daughter board connected to it. However, the 12V rail is usually simply routed there from whatever primary source is powering the development kit - perhaps via a protection diode.

You don't specifically state which Stratix IV development kit you are using but a good look at the schematics should reveal how the 12V gets to the HSMC connector on that particular board. If it is routed directly and you're not supplying power from another source via another route onto the board, then it will be fine to supply 12V via the HSMC connector.

The 3.3V rail is likely to be different. On all the development boards I'm aware of, that have HSMC connectors, the 3.3V rail is generated on the development kit. You should not attempt to supply 3.3V to the development board, via the HSMC connector, if this is the case for your kit. Doing so will clearly result in unwanted contention and could damage the dev kit or your board.

If you identify which kit you're using I can have a quick look over the schematics to confirm whether this is the case.

Regards,

Alex