High density floppy for the A1200

[pandy71]

Hall sensor is used only to detect revolution for floppy - and it exist only on PCB with floppy motor - close to disc (flywheel) - heads are driven by separate motor

CHINON_FB-354


Panasonic_JU-257A605P






For conversion ANY floppy drive can be used - SD or HD - SD is even better (or HD must be forced in SD mode) - there is a lot of analog electronics on floppy board - they purpose is to amplify and equalize then convert to digital, signal that was read from heads - if drive is on HD mode (real HD) those equalization are optimized for 500kbps not 250kbps rate.

Most problems is mechanical nature - floppy must rotate with constant 150rpm - those normal 300rpm floppies are not designed for this so reliability can depend from many things - maybe heavier flywheel can be helpful or maybe current in motor coils must be increased in cleaver way - this is open question and need to be verified.
Additionally also "device ID" must be implemented - Amiga OS sense type of floppy be reading in special mode RDY line - fake device id can be created with help of tiny uC for example.

[Fabie]

pandy71,

thanks for your help and thanks for the pics !!!

ok

also I have a chinon FB354 and it haven't any hall sensor...check the pic
I wonder how this chinon drive manages RPM
also check that on my drive there is a place to connect a HD switch....however it is not there

btw,

you think that add another hall sensor to the opposite side of the motor will work a HD in the AMiga?
or
it needs another modification?

[mech]

fabie,
The hall sensor on the fb354 may be under the flywheel inside.

mech

Originally Posted by Fabie

thanks for the info guys,

btw,

there are only one floppy drive model on the entire world that works as high density drive on the Amiga...it is the chinon FZ357A ????

I think the idiots of commodore order a special custom made High density drive to chinon to make it exclusive
a unique drive that works at 150rpm instead 300

I was doing some experiments on Winuae with HD drives and
my conlusion is that a high density drive to work on any Amiga requires Kickstart 2.0+ ...... so...that chinon high density drive will not works as high density on the A500 or the A2000

Originally Posted by Fabie

pandy71,

thanks for your help and thanks for the pics !!!

ok

also I have a chinon FB354 and it haven't any hall sensor...check the pic
I wonder how this chinon drive manages RPM
also check that on my drive there is a place to connect a HD switch....however it is not there

btw,

you think that add another hall sensor to the opposite side of the motor will work a HD in the AMiga?
or
it needs another modification?

[prowler]

Originally Posted by Fabie

I think that your drive is sony drive with the Amtrade adapter built in
Amtrade:
http://www.amiga-hardware.com/showha...cgi?HARDID=381

it seems that someone in Poland pirated the Amtrade adapter and grab in that PLCC chip....
in other words you have a sony drive + Amtrade adapter

That's an interesting suggestion.

Thanks for the link too!

[rkauer]

Originally Posted by mech

There is also a external dell laptop drive that was adopted for amiga as a HD external floppy:

http://www.cucug.org/amiga/amiinfo/reviews/DellDX9.txt

i would be curious to know whats inside the dell drive to make it work on amiga's..i would think it would have soemthing simular to the power computing one.

also high density amiga drives work fine on 500/2000 with 2x+ roms like you mention, never thought to try 1.3 but that was long before highdensity drives exhisted i think..

mike

I have one original Toshiba drive here with that funny connector, but never found the pinout to convert it to Amiga...

It resembles very much the Dell unit, but without the Amiga DB23 connector...

[Fabie]

Originally Posted by mech

fabie,
The hall sensor on the fb354 may be under the flywheel inside.

mech

I think you are right
must be inside....I will check that tomorrow cause I haven't find at the moment a correct screwdriver to dismantle that

[whitebird]

http://www.amiga-hardware.com/showha...cgi?HARDID=381

Does anyone know what's inside the PAL chip? Or at least some principles about the logic?

[prowler]

@whitebird,

Your link above is broken. Use 'Quote' - not cut and paste.

[whitebird]

Sorry.

http://www.amiga-hardware.com/showha...cgi?HARDID=381

[pandy71]

Originally Posted by Fabie

pandy71,

thanks for your help and thanks for the pics !!!

ok

also I have a chinon FB354 and it haven't any hall sensor...check the pic

strange - mine is revision A - not sure is that important or not but on PCB it has spare place for HD sensor so maybe this is some HD capable drive (HD means 150rpm)

Originally Posted by Fabie

I wonder how this chinon drive manages RPM
also check that on my drive there is a place to connect a HD switch....however it is not there

It is probably close to motor winding (probably under flywheel) - i saw few similar solutions but mostly on 5 1/4 drives.

Originally Posted by Fabie

you think that add another hall sensor to the opposite side of the motor will work a HD in the AMiga?
or
it needs another modification?

Ok - for me it is not clear how HD FDD behave in Amiga

When FDD is 150 rpm and when it rotate with 300rpm
I can imagine that HD sensor telling to the FDD - rotate 150rpm - then Amiga sense this after counting INDEX period (INDEX is signal from hall sensor) but it must be a only one pulse for each revolution.

To convert FDD to the slow HD in my opinion this steps must be taken:

- add hall sensor to made situation that motor controller thinks that floppy revolving twice fast so it try to slow revolutions by half (or modify frequency for reference clock - half frequency - half revolutions)

- INDEX pulse must be always taken form original HALL sensor - then it must be routed to the INDEX, additional HALL sensor must be connected in that way that it will not influent for original INDEX

- Device ID must be changed to HD - in some HD adapters it is PAL circuit but cheaper and faster it can be made by using uC

this is electronic side

Most important is how motor can deal wit lower revolutions than previously 300rpm - IMO this is more important than electronics and im afraid that this will be not so simple as electronic.

[pandy71]

Originally Posted by whitebird

http://www.amiga-hardware.com/showha...cgi?HARDID=381

Does anyone know what's inside the PAL chip? Or at least some principles about the logic?

Probably part for Device ID - ie RDY sequence to identify drive as a HD capable - maybe something additional (like TTL similar logic which is in all FDD for Amiga) - both can be replaced by small uC (easier to program in home)

[orange]

Originally Posted by Fabie

can you add a link to that hack please

here: http://aminet.net/package/docs/hard/PCFloppy2Amiga
You need to add magnet, not Hall sensor.

[pandy71]

Originally Posted by orange

here: http://aminet.net/package/docs/hard/PCFloppy2Amiga
You need to add magnet, not Hall sensor.

You can add magnet OR Hall sensor - magnet can't be disabled - Hall sensor can be disabled - also additional magnet can create flywheel unbalanced which can affect reading.

[orange]

well its easier to add magnet, as per instructions on aminet link.
and I doubt such small weight would unbalance it.

[Loedown]

Originally Posted by pandy71

You can add magnet OR Hall sensor - magnet can't be disabled - Hall sensor can be disabled - also additional magnet can create flywheel unbalanced which can affect reading.

The magnet would have to be placed EXACTLY at 180 degress to the other to ensure reliability surely? The rotor of the motor would have sufficient stability to handle a small magnet off the side without going eccentric, after all it already has one.

[pandy71]

flywheel is balanced - so adding additional mass create it unbalanced - unbalancing is probably small but it can create some problems - more important is that adding magnet is fixed solution - adding Hall sensor (ready available from other FDD maybe broken?) FDD work exactly the same but can be disabled in easy way.

So it is easier to add magnet but it is easier to disable Hall sensor when there is need for this.

[Loedown]

Originally Posted by pandy71

flywheel is balanced - so adding additional mass create it unbalanced - unbalancing is probably small but it can create some problems - more important is that adding magnet is fixed solution - adding Hall sensor (ready available from other FDD maybe broken?) FDD work exactly the same but can be disabled in easy way.

So it is easier to add magnet but it is easier to disable Hall sensor when there is need for this.

If you look at a flywheel they already have a magnet attached, AFAIK there's no counterbalance in place on the flywheel to offset the low revolutions and small mass.

Adding a second HES in parallel means that the current supply will have to be doubled, this may cause issues, plus you will need a way to isolate the output of one HES from the other.

[pandy71]

Originally Posted by Loedown

If you look at a flywheel they already have a magnet attached, AFAIK there's no counterbalance in place on the flywheel to offset the low revolutions and small mass.

it is balanced by design

Originally Posted by Loedown

Adding a second HES in parallel means that the current supply will have to be doubled, this may cause issues, plus you will need a way to isolate the output of one HES from the other.

modern Hall sensors like this on JU257 are low current with all on board (they produce valid digital signal and they are cheap)

Diodes isolate quite well - but some uC can be used (anyway there is need to use some uC or CPLD or PAL to deal with some RDY device id).

Magnet is cheaper and simpler but is not flexible as additional Hall sensor.
Also when i read datasheets for spindle drivers maybe there no need to glue magnet or put additional HES - still searching for some FDD schematics to see how they deal with all logic inside FDD.

[Fabie]

Originally Posted by orange

here: http://aminet.net/package/docs/hard/PCFloppy2Amiga
.

thanks for the link !!

I have readed the docs and there are some useful information and 2 useful proggys there to make a high density drive for the Amiga


it seems that to make a high density drive 2 steps must to be made

1: put the drive to 150 rpm when a high density disk is inserted

2: Ready signal must flip-flop


***for the step 1

we can add a extra sensor like pandy71 said or temporary add a magnet on the opposite side of the flywheel

of course the magnet solution is temporal (for test purposes )cause if anybody adds one magneto on the flywheel the drive will be High density only because there is no way to disconnect it to return to double density

we can check if the drive spins at 150 rpm using this program "drivespeed"
the program works great...I tested the program on winuae


**** for the step 2

the ready signal must flip-flops and there is a program to check if flip-flops...the program is named "DriveID"

this maybe can be solved in a easy way connecting the READY signal to DATA or connecting READY to GROUND or connecting READY to PIN 8 or PIN 10

maybe works because the author also says that for DOUBLE DENSITY .....READY signal must be LOW...but everybody know that READY signal can be disconnected or connected to pin 10 with a diode ....and works anyways in double density

so...maybe that fllip-flop for high density on READY signal is not so strict....we need to experiment adding a circuit or connecting READY signal to any place and check if works

[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)