I remember reading an article eons ago about the tech used for OCR at USPS in what I'm pretry sure was Wired. If I remember correctly, on each sorting line they were using something like 10 dual or quad 200 MHz Pentium Pro systems to accomplish the ultra high speed recognition that they required. That amount of computing power was absolutely mind bending to me at the time, now days it's laughable, a Raspberry Pi would blow it out of the water.