I am now running an i7 3770 with a GA-Z68X-UD3H-B3 (rev 1.3) motherboard on BIOS U1l. VT-d seems to work, I can successfully pass PCI devices to a QEMU instance.
Modern Intel CPUs have the North bridge integrated in the CPU package. Thus, at least for the Sandy Bridge and Ivy Bridge CPUs, the VT-d functionality is provided by the CPU itself (the hardware part). The BIOS must still be configured to provide the necessary information toe the host (software). There does not seem to be an additional hardware requirement if I am not mistaken.
(source: pure guess-work and anecdotal evidence from myself)