High density floppy for the A1200

[Fabie]

Originally Posted by pandy71

After reading datasheet for motor driver http://www.alldatasheet.com/view.jsp?Searchword=LB1813 seems that Hall or magnet can be not important at all (this pulse can be generated in electronic way if needed)

but that is a much complicated task
the easy solution must be the hall sensor on the opposite side like you said
btw
I just purchased a lot of untested 3.5hd pc drives by 10€ to experiment
it seems that some drives works and other not works
but tomorrow I will do some experiments
the first experiment I will do will be placing a magnet on the opposite side of the flywheel and check if RPM spin down to 150

[Loedown]

Originally Posted by pandy71

After reading datasheet for motor driver http://www.alldatasheet.com/view.jsp?Searchword=LB1813 seems that Hall or magnet can be not important at all (this pulse can be generated in electronic way if needed)

Precision is the key, the motor is reasonably precise but what happens when it falters ever so slightly from your timing?

[Loedown]

Originally Posted by Fabie

but that is a much complicated task
the easy solution must be the hall sensor on the opposite side like you said
btw
I just purchased a lot of untested 3.5hd pc drives by 10€ to experiment
it seems that some drives works and other not works
but tomorrow I will do some experiments
the first experiment I will do will be placing a magnet on the opposite side of the flywheel and check if RPM spin down to 150

I don't think it will personally, I believe the logic controller will suggest that the drive is spinning too slow and give an extra kicking pulse after x amount of degrees, but without a thorough knowledge of floppies, this is just my assumption.

[Ratte]

100% working hd-floppy-fix by terminal-entry.de (reptile)

http://www.terminal-entry.de/amiga/eng/floppyfix.html
http://www.terminal-entry.de/amiga/d...floppy-fix.pdf(page 2 - english)
http://www.terminal-entry.de/amiga/d...ds/ffixmod.pdf(page 4-6 - english)
http://www.terminal-entry.de/amiga/d.../floppyfix.rar

[Fabie]

Originally Posted by Ratte

100% working hd-floppy-fix by terminal-entry.de (reptile)

http://www.terminal-entry.de/amiga/eng/floppyfix.html
http://www.terminal-entry.de/amiga/d...floppy-fix.pdf(page 2 - english)
http://www.terminal-entry.de/amiga/d...ds/ffixmod.pdf(page 4-6 - english)
http://www.terminal-entry.de/amiga/d.../floppyfix.rar

yes ..this is another high density adapter for the Amiga
seems similar to the Amtrade adapter

also here is a video demostration...

http://www.a1k.org/download/area51/OLD/HDFloppyFix.mpg

they show in the video the intsall of MSDOS 6.22 and windows 3.11 and MACOS and AtariST using high density disks

however I'm interested in create my own 1 disk version of some games
some games can be 1 disked and that's funny for me
also it seems that if you have a high density drive you can create your own disks from ipf files using the tool WWARP
WWARP support high density drives in certain games

I just created my original Turrican 3 disk using high density drive in winuae and works....
so if works in winuae should works on a real Amiga with a high density floppy

[whitebird]

This hd-floppy-fix looks very similar to the Amtrade.

No hall sensor or magnet...

If only we could know what are those floppy drive modifications... Then it would be possible to generalize to other drives.

[Ratte]

uhhh ... lucky break
http://www.amigafuture.de/album_pic.php?pic_id=16051
the actual online amiga future 69 ... they tested the floppy-fix

[Ratte]

Originally Posted by whitebird

This hd-floppy-fix looks very similar to the Amtrade.

No hall sensor or magnet...

If only we could know what are those floppy drive modifications... Then it would be possible to generalize to other drives.

try the links i posted, there is everthing described in english
all modifications, the pcb, the function ... everything

and its better than the amtrade ... the floppyfix worked on an a1000
(i did the a1k.org testmovie .. )

[FOL]

Originally Posted by Ratte

uhhh ... lucky break
http://www.amigafuture.de/album_pic.php?pic_id=16051
the actual online amiga future 69 ... they tested the floppy-fix

What became of it?

[Ratte]

They searched for a reseller, but had no luck.
As far as I know ACube and/or Vesalia received some samples for testing.
If you are interested in for AmigaKit, I can contact the related persons.

[Fabie]

Originally Posted by whitebird

This hd-floppy-fix looks very similar to the Amtrade.

No hall sensor or magnet...

If only we could know what are those floppy drive modifications... Then it would be possible to generalize to other drives.

you are right...if we could know....
seems the adapter modify the motor clock or the oscilator clock or something like that
something secret and undocumented

[Fabie]

Originally Posted by Ratte

try the links i posted, there is everthing described in english
all modifications, the pcb, the function ... everything

and its better than the amtrade ... the floppyfix worked on an a1000
(i did the a1k.org testmovie .. )

the documents you linked are the modifications for the TEAC drive that works with the adapter
nothing says about how the adapter works and there aren't schematics

[prowler]

Originally Posted by Fabie

the documents you linked are the modifications for the TEAC drive that works with the adapter
nothing says about how the adapter works and there aren't schematics

Hmm... The ffixmod document is really very limited in scope. I have a TEAC FD-235HF unit (a 4240), and the pcb is quite different.

[whitebird]

Yes Fabie, I meant it exactly as you said. The manual explains what to change from a practical point of view. But it should be nice to know the principle, which will allow to apply to other drives even if the PCB is different.

[pandy71]

Originally Posted by Fabie

but that is a much complicated task
the easy solution must be the hall sensor on the opposite side like you said

No, i was wrong - additional pulse is not useful at all - so my fault - Sorry!

Originally Posted by Fabie

btw
I just purchased a lot of untested 3.5hd pc drives by 10€ to experiment
it seems that some drives works and other not works
but tomorrow I will do some experiments
the first experiment I will do will be placing a magnet on the opposite side of the flywheel and check if RPM spin down to 150

Magnet or Hall sensor is not needed - please scan PCB (make photo?) for all IC used for this FDD - i will try to find some useful data.

At first clock used for frequency reference must be half of normal - motor driver use FG coil to detect speed for flywheel - Hall sensor is probably used only for generating INDEX pulse (once per rev) - maybe it is also for R/W amp as a gate but can be verified on schematics and data sheets for IC.
Second - RDY must be Device Self ID capable (uC like small AVR or PIC seems to be OK for this - You can put all logic for MOTOR ON ans DISK SEL on uC + add all switching for 300/150 maybe even generation for reference frequency - if frequency can be programed it open world for variable speed R/W - Apple floppies can be fully read or write)

[Zetr0]

This is indeed fascinating stuff!

I have just looked through the AmigaGuide of the PCHD-FDD to Amiga FDD - it looks quite simple to do indeed.

just need to check my bits boxes for some F74 flipflops and some inverters...

[rkauer]

A simple approach is:

1- give the Amiga the HD stream to show the drive as HD capable.

2- hold the data to a point the Amiga can cope with it. This can be achieved by issuing several hold data (~wait) signals to the floppy as the Amiga can't manage the through output of the floppy.

[pandy71]

Originally Posted by rkauer

A simple approach is:

1- give the Amiga the HD stream to show the drive as HD capable.

So this is unclear for me - i can understand how Device Self Id works but how Amiga distinguish between HD and SD floppy if there is no external signalization for HD - i assume that INDEX is measured - time between two INDEX pulses tell Amiga that floppy revolve 150 (HD) or 300 (SD) rpm?
Then adding magnet or Hall sensor we can destroy this detection

Originally Posted by rkauer

2- hold the data to a point the Amiga can cope with it. This can be achieved by issuing several hold data (~wait) signals to the floppy as the Amiga can't manage the through output of the floppy.

So this was one of my ideas - even some shift (FIFO) register made from DRAM like 41256 or better 411000 (1 mbit DRAM) can be used to store whole track from Index to Index - large DRAM can be used to oversample data (2x - 8x oversample can help with reading and writing data - it reduce uncertainty and error introduced in conversion), detection for half full/half empty, start write data stored in FIFO after half full (twice slower transmission to HD disk from Amiga than should be), start read from FDD by amiga also with similar rule (data transfered to and from floppy with 500kbps but Amiga is capable only to made 250kbps).
Latency is always half time between Index pulses.

Something similar to this:
http://www.nalanda.nitc.ac.in/indust...pp/xapp030.pdf

[Fabie]

I found useful information:

Floppy drive rotation adjustment::

There have been some questions about adjusting the rotation rate of floppy drives. Floppy drives rotate the floppy on a spindle, which is driven by some motor. Many drives allow for adjusting that speed via a small pot (potentiometer, a variable resistor) on the circuit board connected to the spindle motor. AC powered spindles don't have an adjustment, the AC line frequency and the mechanics set the speed.

That spindle often had a decal or lable which consisted of a series of black bars, radially around the edge of the spindle, a kind of star-burst pattern. Some of them were labled "60" and "50" with slightly different patterns. Typical rotation speeds are 300 RPM and 360 RPM, depending on the drive size and density of the diskette's format.

Those lables are actually stroboscopic patterns. If you use a neon lamp or some fluorscent lamps, the 60 HZ (or 50 HZ) line current variations in the lamp would cause the rotating pattern to stand still, IF the drive was at speed. If it was slow or fast, the pattern would appear to rotate slowly. The tech would adjust a small pot to change the speed. Most older floppy drives are not crystal controlled.




more info here:

http://www.retrotechnology.com/herbs_stuff/drive.html

[Fabie]

continuation of my last post

here are 2 drives I have now which have that potentiometer or variable resistor which talk about the document I posted
in the pic I marked with a red circle
I will check later if that potentiometers can regulate the motor speed
I will use the program "drivespeed" from PCFloppy2Amiga.lha to check if is possible