lloyd@ficc.ferranti.com (greg lloyd) (06/13/90)
I need some basic information on IBM-type disk controllers.
First, correct me if I'm wrong:
o 1.2Meg floppy drives rotate faster than 360K drives
(360 RPM vs. 300 RPM).
o 1.2Meg drives are similar to 8" DSDD drives with respect to
rotation and capacity. In many cases, you can replace 8"
DSDD drives with 1.2Meg 5.25" drives (although 8" may support
slightly less than 80 tracks).
o When writing to a 360K disk in a 1.2Meg drive the data rate
must be faster than when writing to a standard 360K drive.
Now the questions:
o Why do the 1.2Meg and 1.4Meg floppy controllers have so much more
hardware than the 360K/720K ones? Is it because data separation
is trickier for the higher density drives?
o Many 360K floppy controllers are very small (about 8 chips - standard
74LSxx and a 765) with very few discrete components. Others
(especially the old true-blue IBM ones) have quite a bit of analog
circuitry. What's the purpose of all the analog stuff and why do
both controllers appear to work the same?
Thanks in advance for replying.
--------------------------------------------------------------------
J. Greg Lloyd
Systems Application Engineering
3655 Westcenter Dr. Houston, TX 77042
UUCP: uunet!ficc!lloyd ph: (713) 274-5260
--------------------------------------------------------------------