HD Tach is a low level hardware benchmark for random access read/write storage devices such as hard drives, removable drives (ZIP/JAZZ), flash devices, and RAID arrays. HD Tach uses custom device drivers and other low level Windows interfaces to bypass as many layers of software as possible and get as close to the physical performance of the device possible.
HD Tach seems to show much lower scaled results than the other benchmarks today, which was something we also noticed with the Corsair F40 drives during previous testing. In regards to performance differences however the 4 Intel drives score 110mb/s more than the dual Sandforce based Corsair units.