Cromemco 4FDC, How do you format a disk?

From: Bill Sudbrink <bill_at_chipware.com>
Date: Tue Jul 27 17:46:25 1999

> You'll need to spend a bit of time studying out
> how the controller you're using handles the drive
> select or even a cable select if it has separate
> selection on the 34 and 50-conductor cables, and
> whatever it does to manipulate the clock extraction
> circuits to derive the appropriate clock for whatever
> data rate you're wanting. BE CAREFUL! Some controllers
> switch the clock frequency as they make whatever
> assumptions they may make about the nature of what's on
> each cable. In order to drive 3.5" diskettes, you need
> to fool the controller and software into believing it's
> talking to a drive on the 50-pin cable. Though the 8"
> drives have only 77 tracks, they have the 360 rpm spin
> rate and most other parameters in common with the little
> teensy drives. If your controller switched the clock
> assuming its top data rate will be 250 kbps, you may
> have problems.

According to the docs, you have to tell the controller
which drive type it is talking to (bit 4 at I/O address
34 hex). Looking at the schematics, it sure looks like
it blindly shoots signals to both connectors. FDAT is
connected to pin 30 on the 34 pin header and pin 48 on
the 50 pin header. Hmmm... what's going on here? Pin 48
is SEP DATA, used with hard sectored drives isn't it?
Pin 50 is connected to FCLK as well.

What gives?
Received on Tue Jul 27 1999 - 17:46:25 BST