speaking of 3.5" floppies, is 720K R.I.P.?

[Chris Elmquist]

On Sunday (02/01/2009 at 11:56PM -0800), Chuck Guzis wrote:
> On 1 Feb 2009 at 10:11, Chris Elmquist wrote:
> 
> > What's particularly nasty is that I chose these drives, Samsung SFD-321B,
> > because I had a recent datasheet that clearly showed they supported
> > this mode--  until of course they arrived and the switch/sensor is not
> > even installed!
> 
> Chris, the OEM manual for the SFD-321B is online at:
> 
> www.techtravels.org/amiga/SAMSUNG-SFD321B-070103.pdf 
> 
> I note that they do use pin 2 as a density select pin and the OPA and 
> OPB PCB jumpers to determine the operating mode.  You might want to 
> play with this a bit to see if you can coax it into operating in 2D 
> mode.
> 
> Whatever, please report back because I note that these drives are (1) 
> cheap and (2) have a provision to supply a READY signal instead of 
> DISK CHANGE.  That could come in useful.

yes... I studied the OPA and OPB jumpers, hooked them up, and no joy.
The actual density selector switch or optical sensor is missing from
the drives I received.  So, there is no way for it to know that the
low-density media has been installed.  It needs this input along with
the density select coming from PIN 2 on the interface to decide what
mode to go into.  If all the parts were there, then the PIN 2 would
choose between 2.0 MB and 1.6 MB (raw) modes (and actually change the
RPM to 360 when going to 1.6 MB mode) but that would only happen if a
low-density disk could be detected.

So, I think they have cheaped out on us with these particular drives.
I mean, they are cheap to start with ($7 ea) but this appears to be an
extreme situation.  I think they can only do high density, 1.44MB format.

I've also found a warning in the CatWeasle documentation that this drive
is not compatible with it and a claim that they are high density only.
Which, I think I have proven again.

I'm now exploring both Sony MPF920 and Alps 635H drives...  they look
like possible candidates at about the same price point.

Chris

-- 
Chris Elmquist
mailto:chrise at pobox.com