Siemens FDD200 configuration

Chuck Guzis cclist at
Wed Apr 8 11:21:36 CDT 2015

On 04/08/2015 12:50 AM, supervinx wrote:
> Hi! Got two FDD200, 8" drives. I revised their config with the manual
> handy. They seem OK for my needs (reading soft sectored IBM disks)
> except for a thing. They are configured for radial selection but with
> dedicated SELECT lines for heads/side. The first disk responds to
> SELECT lines 0 and 2, respectively for HEAD 0 and 1. The second disk
> responds to SELECT lines 1 and 3, for HEAD 0 and 1. This can easily
> be reverted moving a soldered wire jumper. I'd like to know why they
> were configured that way. I'll use the FDADAP adapter, BTW. Thanks!

The most likely explanation is that the controller used was most likely 
a single-sided one, with no separate head select line.  (Recall that 
double-sided floppies arrived on the scene a few years after 
single-sided ones).   So, the solution for double-sided floppies on a 
single-sided controller was to make a drive appear as two single-sided 
units.   Not terribly uncommon.


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