8 Apr
2015
8 Apr
'15
12:21 p.m.
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.
--Chuck