On 10 Nov 2008 at 9:54, Al Kossow wrote: Back in the early 70's, part of a QSS we did was warranting the readability of 7080 729-generated tapes of which the customer had many thousands. One of the engineers opined that the approach to tape by CDC and IBM were diametrically opposite and led to some consternation and a bit of drive "tweaking". IBM apparently was a bit sloppy with their writing technology but had very good reading capabilities. CDC did good writing, but their reading wasn't up to IBM's. Or maybe it was the other way around. But for tape motion, IBM used a pinch-roller system, where CDC used a voice-coil valve to swich vacuum between two counter-rotating capstans--one on each side of the head. At least for 7-track, the best drives were the 60x models; the 65x drives used a "cost reduced" valve design and weren't nearly as good. Cheers, Chuck