1 Feb
2009
1 Feb
'09
8:11 a.m.
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.
I needed the 300 rpm, 250Kbps capability to be compatible with the old
5.25" stuff.
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!
Is this true of all 3.5" drives now?
This might explain why 720K 3.5" drives are selling for $285 on eBay :-(
I'd sure like to find a way to force the drive into 250Kbps mode-- I
can't believe the chips don't still support it-- I just need a way to
figure out where the sensor is supposed to connect and hard wire it to
720K mode. Any ideas on how to do that?
Chris
1 Feb
1 Feb
11:56 p.m.
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.
Cheers,
Chuck
2 Feb
2 Feb
5:52 a.m.
On Sunday (02/01/2009 at 11:56PM -0800), Chuck Guzis wrote:
On 1 Feb 2009 at 10:11, Chris Elmquist wrote:
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
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. 
4 Feb
4 Feb
11:58 a.m.
you might try here
http://www.newegg.com/Product/Product.aspx?Item=N82E16821103116
according 2 what i can find it will do 720
On 2/2/09, Chris Elmquist <chrise at pobox.com> wrote:
On Sunday (02/01/2009 at 11:56PM -0800), Chuck Guzis wrote:
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
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.
3:59 p.m.
On Wednesday (02/04/2009 at 11:58AM -0800), Chris Halarewich wrote:
you might try here
http://www.newegg.com/Product/Product.aspx?Item=N82E16821103116
according 2 what i can find it will do 720
Well, they CLAIM to do 720. I actually ordered the SAMSUNG units from
Newegg, after studying the very datasheet for the drives and confirming
they would do 720... only to receive them and find that the design is
not what the datasheet claims. That's my sad story :-)
So, I guess it's spin the wheel and see if Sony has or hasn't decided
to leave the 14 picocents worth of parts off the thing to maximize the
margin on that $7 product.
Chris
--
Chris Elmquist
mailto:chrise at pobox.com
12:21 p.m.
On Mon, 2 Feb 2009, Chris Elmquist wrote:
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.
Wow. The problem is not the missing switch - that can obviously be
jumpered. The first problem is that your drive does not HAVE a low density
mode. When they removed the switch, they also changed it from "high v low"
modes (2.0 v 1.0 raw) to "high density mode" v "NEC high density
mode"
(which would not use that switch anyway.
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.
and with some jumpering 1.3M Japanese high density
Are Teac drives getting that hard to come by?
1:01 p.m.
On 2 Feb 2009 at 7:52, Chris Elmquist wrote:
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.
Just curious, Chris--not that it'll do any good--but what's the chip
used on these drives?
Thanks,
Chuck
5 Feb
5 Feb
5:14 a.m.
On Wednesday (02/04/2009 at 01:01PM -0800), Chuck Guzis wrote:
On 2 Feb 2009 at 7:52, Chris Elmquist wrote:
main brain is: SEMCO SF12021AG
motor control: LB11911
If anyone has a datasheet for the main brain, that would be wonderful.
I struck out searching for such a thing.
Chris
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.
Just curious, Chris--not that it'll do any good--but what's the chip
used on these drives? 
2 Feb
2 Feb
7:13 a.m.
----------------------------------------
From: cclist at sydex.com
To: cctalk at classiccmp.org
Date: Sun, 1 Feb 2009 23:56:43 -0800
Subject: Re: speaking of 3.5" floppies, is 720K R.I.P.?
On 1 Feb 2009 at 10:11, Chris Elmquist wrote:
Hi
I'd given up on finding ones with the /READY signal.
I needed one to add double sided to my Canon Cat. It
had a Canon with a weird 20 pin cable that I just recently
figured out the wiring. I made a circuit with three ttl
chips to recreate the /READY that works well enough.
I had to make a cable translator anyway so I had
a piece of proto board to add the chips on.
I'd found a nice source of cheap 3.5 drives with
the 720K switch at Weirdstuff here in Sunnyvale.
They're mostly Teac FD235HF drives but I like the
Teac drives anyway. The price is right and all
the drives I've bought work fine( $5 ). They're
pulls but I don't let that bother me.
The circuit is simple enough that one could use
a registered PLA but one still needs the drive
current of a 7438. Maybe doubling or tripling
a few outputs would be enough as it is only the
one signal needed for the /READY. I also needed
to recreate the selects and motor signals from
a single select and motor enable.
Dwight
_________________________________________________________________
Windows Live? Hotmail??more than just e-mail.
http://windowslive.com/howitworks?ocid=TXT_TAGLM_WL_t2_hm_justgotbetter_how…
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.
Cheers,
Chuck
10:14 a.m.
On 2 Feb 2009 at 7:13, dwight elvey wrote:
I'd given up on finding ones with the /READY
signal.
I needed one to add double sided to my Canon Cat. It
had a Canon with a weird 20 pin cable that I just recently
figured out the wiring. I made a circuit with three ttl
chips to recreate the /READY that works well enough.
I had to make a cable translator anyway so I had
a piece of proto board to add the chips on.
I've done the same here with an 8-pin PIC (the advantage is that
there are no discrete timing components). The same could probably be
done with one of the 6-pin PICs. But finding drives with a native
READY signal is better.
Cheers,
Chuck
6:11 p.m.
----------------------------------------
From: cclist at sydex.com
To: cctalk at classiccmp.org
Date: Mon, 2 Feb 2009 10:14:57 -0800
Subject: RE: speaking of 3.5" floppies, is 720K R.I.P.?
On 2 Feb 2009 at 7:13, dwight elvey wrote:
Hi
The only timing I had was for powerup reset. Just a cap, resistor
and diode. The rest is digital. I use an edge on diskchange
to clear and the first index to set. It isn't perfect as one
could stick a disk in and turn the motor on and then remove
without stepping. This is not likely on the Cat because
it always uses the disk for a dump ( multiple tracks ).
The Teac holds the index until ready.
Dwight
_________________________________________________________________
Windows Live? Hotmail??more than just e-mail.
http://windowslive.com/howitworks?ocid=TXT_TAGLM_WL_t2_hm_justgotbetter_how…
I'd given up on finding ones with the /READY
signal.
I needed one to add double sided to my Canon Cat. It
had a Canon with a weird 20 pin cable that I just recently
figured out the wiring. I made a circuit with three ttl
chips to recreate the /READY that works well enough.
I had to make a cable translator anyway so I had
a piece of proto board to add the chips on.
I've done the same here with an 8-pin PIC (the advantage is that
there are no discrete timing components). The same could probably be
done with one of the 6-pin PICs. But finding drives with a native
READY signal is better.
Cheers,
Chuck
6:40 p.m.
On 2 Feb 2009 at 18:11, dwight elvey wrote:
The only timing I had was for powerup reset. Just a
cap, resistor
and diode. The rest is digital. I use an edge on diskchange
to clear and the first index to set. It isn't perfect as one
could stick a disk in and turn the motor on and then remove
without stepping. This is not likely on the Cat because
it always uses the disk for a dump ( multiple tracks ).
The Teac holds the index until ready.
Mine was for 5.25" drives; basically it waits for 2 index pulses
spaced within 10% of the nominal speed of the drive before asserting
READY. Could probably also be done with a couple of one-shots, but I
hate one-shots--and the PIC is smaller.
The nice thing is that the same PIC setup can also simulate hard-
sectored diskettes. The PICs are rated to sink/source 25 ma on any
I/O pin, not to excees 125 ma for all pins. A little dodgy for 150
ohm pullups (33 ma at 5v), but I've had no problems thus far.
Cheers,
Chuck
4 Feb
4 Feb
4:14 p.m.
On Monday (02/02/2009 at 06:40PM -0800), Chuck Guzis wrote:
The nice thing is that the same PIC setup can also simulate hard-
sectored diskettes. The PICs are rated to sink/source 25 ma on any
I/O pin, not to excees 125 ma for all pins. A little dodgy for 150
ohm pullups (33 ma at 5v), but I've had no problems thus far.
I have been trying to do this exact thing... simulate 10-hole hard
sectored floppies with the 3.5" drive.
I'm finding it much more difficult than I expected. It seems that the
speed of these drives is not very constant. So, when I trigger off the
real index pulse from the drive and then generate very accurately timed
pulses simulating the 10 other holes, it appears that they are not lining
up with the data some number of rotations later.
The result is a high number of soft errors during read back.
My simple plan was to just watch for the real index hole from the selected
drive and then generate the synthetic ones back to the controller until
the drive was deselected. I could see I had a timing problem which I
initially blamed on the microcontroller's RC clock (I am using an ATMEL
AVR instead of a PIC). So, I improved this in various increments,
ending up with a +/- 50ppm osc can and at each increment of improving
the stability of the clock, my soft errors INCREASED!
I'm now reworking the whole design and I'm going to keep the soft sectored
drive always selected, always motor on and continually watch the real
index pulses and compute the instantaneous RPM. From that, I'll generate
the pseudo index pulses which will hopefully better match the current
speed of the drive. The pseudo pulses and all the other drive signals
will be externally gated onto the floppy bus since I need to keep the
emulating drive always active-- and I want to emulate two drives at the
same time. Kind of a pain but I don't see how else to get there now.
Any suggestions on what I am missing?
Chris
5 Feb
5 Feb
7:02 a.m.
----------------------------------------
Date: Wed, 4 Feb 2009 18:14:02 -0600
From: chrise at pobox.com
To: cctech at classiccmp.org
CC: cctalk at classiccmp.org
Subject: Re: speaking of 3.5" floppies, is 720K R.I.P.?
On Monday (02/02/2009 at 06:40PM -0800), Chuck Guzis wrote:
Hi Chris
I was recently looking at my Teac drive's index pulse to see how it
worked relative to the drive going ready ( the problem of trying to
find a way to recreate the /Ready signal ).
One thing I noticed was that the leading edge of the index pulse
was as accurate as my scope could show but the trailing edge was
all over the place.
My thinking is that the drive is controlled by a servo loop.
The leading edge is when a crystal clock says the pulse is suppose
to start and the trailing edge is when the actual edge is detected.
If one timed the length of time between the two edges, one would
then know the corrective response of the loop.
As an example, if the pulse was long, you'd keep a similar software
wheel rotating that you apply a correction to by the amount the
pulse was long.
It would be this internal software generated wheel that you'd use
to create the index pulses from.
You need the code to watch the drive to determine the parameters
of the control system, gain, dampening and intertia.
If done this way, I suspect that one could get very close to
the right index pulse spacing.
Dwight
_________________________________________________________________
Windows Live?: Keep your life in sync.
http://windowslive.com/howitworks?ocid=TXT_TAGLM_WL_t1_allup_howitworks_022…
The nice thing is that the same PIC setup can also simulate hard-
sectored diskettes. The PICs are rated to sink/source 25 ma on any
I/O pin, not to excees 125 ma for all pins. A little dodgy for 150
ohm pullups (33 ma at 5v), but I've had no problems thus far.
I have been trying to do this exact thing... simulate 10-hole hard
sectored floppies with the 3.5" drive.
I'm finding it much more difficult than I expected. It seems that the
speed of these drives is not very constant. So, when I trigger off the
real index pulse from the drive and then generate very accurately timed
pulses simulating the 10 other holes, it appears that they are not lining
up with the data some number of rotations later.
The result is a high number of soft errors during read back.
My simple plan was to just watch for the real index hole from the selected
drive and then generate the synthetic ones back to the controller until
the drive was deselected. I could see I had a timing problem which I
initially blamed on the microcontroller's RC clock (I am using an ATMEL
AVR instead of a PIC). So, I improved this in various increments,
ending up with a +/- 50ppm osc can and at each increment of improving
the stability of the clock, my soft errors INCREASED!
I'm now reworking the whole design and I'm going to keep the soft sectored
drive always selected, always motor on and continually watch the real
index pulses and compute the instantaneous RPM. From that, I'll generate
the pseudo index pulses which will hopefully better match the current
speed of the drive. The pseudo pulses and all the other drive signals
will be externally gated onto the floppy bus since I need to keep the
emulating drive always active-- and I want to emulate two drives at the
same time. Kind of a pain but I don't see how else to get there now.
Any suggestions on what I am missing?
Chris
10:11 a.m.
On 4 Feb 2009 at 18:14, Chris Elmquist wrote:
I'm finding it much more difficult than I
expected. It seems that the
speed of these drives is not very constant. So, when I trigger off the
real index pulse from the drive and then generate very accurately timed
pulses simulating the 10 other holes, it appears that they are not lining
up with the data some number of rotations later.
I can't say much about any experience with 3.5" drives in this; I've
been using 5.25" units and measuring the speed with every rotation.
Given the low mass of 3.5" direct-drive motors and media, I can well
imagine that speed variations are all over the place. I wonder if
one can tap into the PLL used to control the motor--there should
certainly be enough information there to determine short-term speed.
However, after 5.25', I'm going to an all-electronic solution;
basically a sampling plug-in replacement for a drive. I figure that
rusty goo smeared on plastic cookies is not only going to be harder
to find, but show a pronounced decline in quality as remaining
production gets shoved out to the margins of the commercial world.
I have customers who would probably kill to replace the floppy drives
in their equipment.
Cheers,
Chuck
The result is a high number of soft errors during read back.
My simple plan was to just watch for the real index hole from the selected
drive and then generate the synthetic ones back to the controller until
the drive was deselected. I could see I had a timing problem which I
initially blamed on the microcontroller's RC clock (I am using an ATMEL
AVR instead of a PIC). So, I improved this in various increments,
ending up with a +/- 50ppm osc can and at each increment of improving
the stability of the clock, my soft errors INCREASED!
I'm now reworking the whole design and I'm going to keep the soft sectored
drive always selected, always motor on and continually watch the real
index pulses and compute the instantaneous RPM. From that, I'll generate
the pseudo index pulses which will hopefully better match the current
speed of the drive. The pseudo pulses and all the other drive signals
will be externally gated onto the floppy bus since I need to keep the
emulating drive always active-- and I want to emulate two drives at the
same time. Kind of a pain but I don't see how else to get there now.
Any suggestions on what I am missing?
Chris
2 Feb
2 Feb
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
5578
days inactive
5582
days old
15 comments
5 participants
participants (5)
-
cclist＠sydex.com -
chrise＠pobox.com -
cisin＠xenosoft.com -
dkelvey＠hotmail.com -
halarewich＠gmail.com