"intelligent" disk drives

The Atari 8bit computer disk drives, were were SIO Bus (Serial I/O Bus - what amounts to a very early version of USB) were the 810 and Atari 1050 disk drives which used 6507's for communicating to/from the host Atari PC as well as a WD floppy controller (Atari 810 - 1771, Atari 1050 - 2793 or 2797 depending on revision of model) The later XF551 Atari 8bit disk drives used an 8040/8050 and WD 1772 Everything on the Atari SIO bus were essentially "Intelligent Peripherals" that had to have their own CPU chip in order to talk across on the SIO Bus. It was a nice design and its over-sized trapezoid connectors made hooking up (Daisy Chaining) peripherals an easy no-brainer/no mistake setup. However, these intelligent peripherals ended up hurting the Atari 8bit line because of their inherently high expense. It was interesting - in 1983 you could buy an Atari 800XL computer for around $299, but the 1050 XL series disk drives cost $359 or higher, so the cost of owning a disk drive was a luxury, owning two such devices was a rare sight to see for many Atari users at the time. The 1772 were also used on most of the 16/32bit Atari ST computers. Atari would later develop a custom IC called "Ajax" for high density floppy drive usage. (Atari IC part#'s C302096, C302434) Curt The Atari XF551 Geoff Reed wrote: