Variation #2 - Drives Supported if a Switch block is Fitted

If a switch block were to be fitted, the switches would be set according to the drive/s attached.

Switch Settings

Switches 1 & 2 configure drive 0 (C:)
Switches 3 & 4 configure drive 1 (D:)

Table Address	Switch Settings for C:	Drive Characteristics	Comment
0	1=on 2=on	Cylinders = 306 / Heads = 2 / WPC = 0 / a step rate of 3 ms is valid	milliseconds, not microseconds
1	1=on 2=off	Cylinders = 375 / Heads = 8 / WPC = 0 / a step rate of 70 µs is valid
2	1=off 2=on	Cylinders = 306 / Heads = 6 / WPC = 256 / a step rate of 70 µs is valid
3	1=off 2=off	Cylinders = 306 / Heads = 4 / WPC = 0 / a step rate of 70 µs is valid	What gets selected if no switch block

The information in the above table was sourced from the book: Upgrading and Repairing PCs, Scott Mueller, 5th Edition, page 761/762/763

That ties in well with what SpeedStor software reports.
On a computer with variation #2 of the controller fitted, if I activate SpeedStor's ROMLIST switch ( i.e. A:\>sstor /romlist ), the result is:

Table	Cylinders	Heads	WPC	Control
0	306	2	0	0
1	375	8	0	5
2	306	6	256	5
3	306	4	0	5