2 Feb
2009
2 Feb
'09
12:50 p.m.
On Sun, 1 Feb 2009, Chris Elmquist wrote:
I don't have an answer for the other
gentleman's query on 720RPM floppies
but I recently discovered that new 3.5" drives appear to no longer support
720K media. I purchased a number of Samsung drives for a project where
I am converting a system with 5.25" drives to use 3.5" and I found that
these drives have left out the media density sense switch all together!
They no longer have any way to detect the lower density, 250kbps media
and run at 500Kbps no matter what is installed.
Try nudging pin 2?
Trace the circuit where it would have been and cut/jumper?
The original IBM PS/2 "1.44" drive was arguably one of the first 1.4M
drives, and did not have a media select switch. The data transfer rate
was set by the controller, and controlled by software.
The "media select" switch can have two basic functions: either switching
to reduced current mode, for which there is usually an input pin on drives
without the switch, or as an output from the drive to tell the controller.
Either should be trivially bypassable if you want to lock the drive into
"720K mode".
--
Grumpy Ol' Fred cisin at xenosoft.com