"intelligent" disk drives

[Tony Duell]

> 
> the C= disk drives were pretty much all smart drives weren't they?  the big dual
> drive units had a controller card in them that was basically a small computer (IIRC)
> 
> also Atari disk drives had a 650x IIRC in them as well as a disk controller chip
> (once again IIRC.)
> 

The Epson TF20 is a double 5.25" drive used with their early laptops 
(HX20, PX4, PX8, etc), it communicates with then over an RS232-level 
serial link at 38400 buad. 

The TF20's controller board is packed with chips. As well as the disk 
controller chip, there's a Z80A, 64K of DRAM (more than the host computer 
in some cases!), a boot ROM that is paged out after the drive unit has 
booted, and lots of glue logic. A daugterhboard contains a 7201 chip and 
the RS232 drivers/receivers.

I am told it boots a modified CP/M from the disk in the A: drive at 
power-on. 

The drives themselves are somewhat interewting, being the Epson 1/3rd 
height units with a voice-coil head positioner.

-tony