Sony MPF920 PC HD Floppy Drive to Amiga HD Floppy Drive Hack

[chrisfi]

Here's an early release of the mod I have been working on and covered in this thread from page 3 onwards.

Note this is Beta so there may be some undocumented features. See below for current known issues/limitations which I will try to update as I get feedback.

However, I and others have tested this mod and it works well as a single drive and in big box Amigas with two drives.

Issues and Limitations

1. ATK reports the drive ID for HD disks as unstable. This issue doesn’t affect normal use.
2. Some NDOS games do not work. This is not caused by the HD modification - see this and 3 below
3. Some Sony floppy drives do not work well with OS 3.1.4 and OS 3.2. This applies to both the basic DD and my HD modifications.
4. Currently the mod is for the Sony MPF920 range of floppy drives only. I intend to experiment on other drives so more may be included under future releases.

Known working drives

Model...........IC2..........Resistor Replaced?
===========================
T/B53.......D9848N..............Yes..............
Z/131.......BA6986FS...........No...............
E/131.......BA6986FS...........No...............

The attached zip has the jed file and instructions. You will need a GAL16V8 PLCC.

The instructions assume you are familiar with modding a Sony drive to work as an Amiga DD drive. If you are not, search for your drive in the Modifying PC floppy drives for Amiga use thread.

[AJCopland]

Nice work, I never thought that'd be possible!

[lesta_smsc]

Thank you for releasing this! This mod has been a very secretive endeavour to the point someone posted they wanted to make some more money off it before they would consider releasing it.

I know there are other mods including one on Aminet I believe but this seems to be a neater solution.

Now flashing GAL... I recall JTAGging a OBD2 connector to flash the GAL16V8D chip (same as the one you're using although this has D on end). I wonder if that could be used as a donor to flash this.

Keep up the good work! I've got quite a few drives here... including Sony MPF920. I currently prefer it for use on Greaseweazle as it was an NOS drive... might convert it.

Would a pic variant instead of PLCC work (cutting off pins to make it sit flat.


Update: Just a thought. Rather than modifying the floppy drives to effectively swap pins (to make PC floppy drive work on Amiga), would it not be better to just have a mini pcb / connector that can slot into the back of PC drive before you attach the floppy drive cable that effectively swaps the necessary pins thereby no need to mod drive at all (or even doing this on a cable directly)

On top of that, adding further circuitry on this board could work for signal interruption to allow GAL chip to work?

[adolescent]

Great work! I need to look through my FDD stash to see if I have the correct model.

[chrisfi]

Originally Posted by lesta_smsc

I know there are other mods including one on Aminet I believe but this seems to be a neater solution.

I have to give credit to Dick Diederik who released the mod on Aminet. His work and the pictures on this thread inspired my mod. It’s recommended reading to those who want to better understand how my mod works.

Originally Posted by lesta_smsc

Now flashing GAL... I recall JTAGging a OBD2 connector to flash the GAL16V8D chip (same as the one you're using although this has D on end). I wonder if that could be used as a donor to flash this.

In theory any version of the GAL/ATF16V8 should work. I’ve used two different variants with 25ns the slowest. However, as they say, your mileage may vary

Originally Posted by lesta_smsc

Would a pic variant instead of PLCC work (cutting off pins to make it sit flat.

If you mean the PDIP variant, then yes, but you won’t be able to reflash a new config later assuming there will be an update……

Originally Posted by lesta_smsc

Update: Just a thought. Rather than modifying the floppy drives to effectively swap pins (to make PC floppy drive work on Amiga), would it not be better to just have a mini pcb / connector that can slot into the back of PC drive before you attach the floppy drive cable that effectively swaps the necessary pins thereby no need to mod drive at all (or even doing this on a cable directly)

On top of that, adding further circuitry on this board could work for signal interruption to allow GAL chip to work?

I had thought about this and I think it is doable, but I haven’t tested the theory. One thing to note is you would still need to make some minor modifications to the drive to get at the signals that aren’t present on the drives connector such as density, osc out, osc in, etc. You could wire these signals to the unused pins on the drives connector to extend to the GAL on the PCB and add a jumper to toggle the drive between PC and Amiga use.

[salteadorneo]

Picking up on a topic from the other thread.
Yes, the mod is not related to the compatibility issue with certain Sony floppy drives and the trackdisk.device in 3.2. This failure happens simply by modifying the floppy drive for Amiga. It has nothing to do with the MOD HD.
The issue is that I have two models of boards that are practically the same and in one it works perfectly and in the other it fails.

I'm going to test the mod with a GAL 16V8 15 to see how it behaves. The tests were done with a 16V8 10.

[hooverphonique]

Originally Posted by lesta_smsc

Update: Just a thought. Rather than modifying the floppy drives to effectively swap pins (to make PC floppy drive work on Amiga), would it not be better to just have a mini pcb / connector that can slot into the back of PC drive before you attach the floppy drive cable that effectively swaps the necessary pins thereby no need to mod drive at all (or even doing this on a cable directly)

Ian Stedman (Steedy) already did designs for this: http://www.ianstedman.co.uk/v2-x-floppy-adaptor/

[fgh]

Originally Posted by hooverphonique

Ian Stedman (Steedy) already did designs for this: http://www.ianstedman.co.uk/v2-x-floppy-adaptor/

Except this new method is for making it an amiga HD drive.

[hooverphonique]

Originally Posted by fgh

Except this new method is for making it an amiga HD drive.

I know, but that wasn't what was asked for in the quoted paragraph as far as I understood it.

[salteadorneo]

Tested the mod with a GAL 16V8D15 and it works the same as with the 16V8D10. The GAL 16V8D15 are somewhat cheaper.
I confirm that the floppy drive modified with the mod is somewhat slower than the Chinon 357A. The Sony has taken 7 minutes and 8 seconds to copy a folder with FileX (about 1.3 megabytes) on a PC-formatted floppy disk. In the original Chinon it took 6 minutes and 52 seconds.

[TommyE]

Hello

First of all great work

But, what am I missing? I tried the mod. on two different Sony 920 drives.
One from 1996 with LML-F1 board and one from 2004 with LML-F32 board. Both have the model # E/131 on the outside sticker.

I can boot the Amiga after the HD mod, but the Amiga is slow to boot, and when Workbench is loaded up, I get DF1:????, DF2:???? AND DF3:????

I'm trying as DF0: in an Amiga 500 with kickstart 2.04

The drives works modded for Amiga use without the HD mod.

Regards
Tommy

[TommyE]

Hello again.

I guessed there is something strange with the READY line, so I hooked up my oscilloscope. I can see that there is activity on PIN3 on the GAL, but nothing on PIN16 that is beeing fed to the floppy.

Any ideas on what may be the cause of that?

Regards
Tommy

[chrisfi]

Hi Tommy,

Hmm, what voltage can your scope see on pins 3 and 16? Whats the part number of the GAL you're using and have you tried another GAL?

Also, if you can boot ATK with the modded floppy drive, put a DD floppy in the drive note the drive ID and do a signal test with the motor on and note both the index pulse period and RDY value. Repeat with a HD floppy in the drive.

[TommyE]

Hello Chris

When you said GAL part number... I looked again and I had several types of the 16v8 type, so I checked my programmers settings and I was missing a B in the type settings.
Burned again, and it worked

Thanks for your help

Tommy

[chrisfi]

Originally Posted by TommyE

Hello Chris

Burned again, and it worked

Thanks for your help

Great stuff and no problem.

Please do feedback any comments, observations or issues as you use it. Hopefully it will be trouble free

[TommyE]

Originally Posted by chrisfi

Great stuff and no problem.

Please do feedback any comments, observations or issues as you use it. Hopefully it will be trouble free

I have been trying it on my rejuvenated A1000 with kick 3.2.1 and Emu68. It seems to be a miss and hit with HD format.
I have read that this might have something to do woth timing and specific drives in newer kickstart versions.

I will try to do some tests with kick 2.05 at some point.

Will also try to see of my A4000 HD drive can work in the Emu68 A1000 at some point.

Regards
Tommy