netnews@sei.cmu.edu (Netnews) (11/06/86)
The discs on the English Electric KDF9 spun at constant speed but had a variable number of sectors per track. The gory details: From: firth@sei.cmu.edu (Robert Firth) Path: sei.cmu.edu!firth speed: 1000 rpm discs: 16 (+ 2 for control) read arms: each arm had 4 heads above and 4 below the platter, and could be moved to 64 positions, giving 256 tracks per surface or 512 per disc. blocking: The inner half of each surface had 8 sectors per track and the outer half had 16; each sector was 40 words and each word was 48 bits. Total capacity was therefore about 3.9 Mword. Transfer rate was 10600 word/sec for the outer zone and half that for the inner zone; average latency was about 240ms. It was a beast to program, too!