My reader is plugged directly into the usb on the back of my emac. I have tried an old card reader with a CF card and that mounts as will a 256mb card but I know it does not work with SDHC cards. I have tried my newer and newest card readers and neither of them will mont the CF or SD or SDHC cards so maybe I've been unlucky with the new reader and it is faulty. I bought it cheap off ebay. Maybe its a case of you get what you pay for?