Replacing drives on classic systems was Wild-hair floppy drive question

Randy McLaughlin cctalk at
Mon Jun 13 21:01:09 CDT 2005

When replacing drives in classic systems there are some things to keep in 

Newer drives are mainly compatible but not 100%.

Today we can go to the local store buy a drive (floppy to hard drive) plug 
it in and expect it to just work.  Things have changed.

To install a drive in a classic computer it is easiest with documentation. 
With newer drives study the use of "modified" pins on 34 pin connector (2, 
10, 12, 14, 16, and 34 especially).

I have some useful information on disks and disk drives on my website.

Pin 2 - 8" drives low to reduce write current for some tracks (but not 
all) - PC drives high to reduce write current for the entire drive and 
optionally change rotational speed.

Pin 10 - Classic 5.25" DS0 - PC motor on for drive A on controller side, 
unused on drive side (part of cable twist).

Pin 12 - Classic 5.25" DS1 - PC DS for drive A (part of twist).

Pin 14 - Classic 5.25" DS2 - PC DS for drive B (part of twist).

Pin 16 - Classic 5.25" Motor on - PC motor on for drive B for controller 
always motor on for drive (part of cable twist).

Pin 34 - Sometimes ready sometimes disk change, either verify or cut.

There are lots of other options to take into account all I can say is don't 
expect to add a drive to a classic system and expect it to just work.  Often 
it takes a lot of head scratching and reading.  Please note I did not 
mention that there are lots of jumperable optoins on many systems.


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