Those cards REQUIRE a 4pin power plug to just turn on by what I have read. (Nice cards, Damn fine if you ask me!) However, it sounds like Evehsham setup this system to not take the utmost of the cards. If you feel comfortable doing this, open the case and see if there is a power connector from the PSU connected to each card. If not, there is an issue, if so then it may be in the cards them selves.

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