Modifying PC floppy drives for Amiga use

[alenppc]

Here's an update. Bought a bunch of brand new DSDD disks on Ebay, unformatted. They format wonderfully with original Amiga drives, modded Chinon PC drives and the like. The Samsung drives still refuse to format them. Not only that, they won't format them even when connected to a PC without any mods.

Conclusion: these drives are pure garbage. I am amazed that Samsung was allowed to sell this crap! They are essentially floppy-readers only, they can't write. Amazing. So yeah, I wasted money on them but it was a valuable lesson learned... stay away from Samsung.

[r.cade]

Some HD drives won't write to DD disks, you found one.

It probably does not have the HD/SD detect circuitry anymore, to save some pennies. It's not like it's needed in modern times, except for using extinct media.

They stopped making cars that will accept "regular" (non-unleaded) gas anymore, also.

[prowler]

Originally Posted by alenppc

Here's an update. Bought a bunch of brand new DSDD disks on Ebay, unformatted. They format wonderfully with original Amiga drives, modded Chinon PC drives and the like. The Samsung drives still refuse to format them. Not only that, they won't format them even when connected to a PC without any mods.

Conclusion: these drives are pure garbage. I am amazed that Samsung was allowed to sell this crap! They are essentially floppy-readers only, they can't write. Amazing. So yeah, I wasted money on them but it was a valuable lesson learned... stay away from Samsung.

But... but my KryoFlux was supplied complete with a Samsung SFD-321B/EF floppy drive!

[alenppc]

@r.cade
This is the first time I hear of this. I don't think the analogy is correct, this is as idiotic as making blu-ray 2.0 drives that refuse to read 1.1 discs... Is there a way to add this circuit back somehow?

@prowler
It's possible that this wonderful "feature" is not present on your revision, as on my (TA) revision. I suppose one could still use these drives for reading floppies and use an external drive for writing them. Gotta try formatting an HD floppy on the PC with this fantastic drive, to see whether it makes a difference.

[Arnie]

I thought i would share this with you. I have just modified a Panasonic JU-256A428P following the instructions from post #226 by dJOS.

[lesta_smsc]

Would be useful if these 'guides' could be collated into a Downloads area as .pdf or similar

[dJOS]

Originally Posted by Arnie

I thought i would share this with you. I have just modified a Panasonic JU-256A428P following the instructions from post #226 by dJOS.

Cool, but kipper2k did the hard work figuring out the original mod so I can't take any credit.

[Arnie]

Originally Posted by dJOS

Cool, but kipper2k did the hard work figuring out the original mod so I can't take any credit.

Ah OK but, if you hadn't shown a pic with pins 1&2 bridged then I would have followed kippers pic and bridged pins 1&3, so I personally thank both Kipper and you....Thanks

[dJOS]

Originally Posted by Arnie

Ah OK but, if you hadn't shown a pic with pins 1&2 bridged then I would have followed kippers pic and bridged pins 1&3, so I personally thank both Kipper and you....Thanks

The irony is cant remember why I bridged 1 & 2 instead of 1 & 3!

[Mrs Beanbag]

Was looking at an Alps DF354H on ebay yesterday, seems quite an easy one to mod and maybe an instructive project. But I'm still intrigued as to why it's so difficult to get a drive to work properly as HD, however when I look at the pinouts I'm now puzzled as to how it ever works at all, because we need pin 2 (density select) rewired to the Disk Change signal... so where is our density select signal supposed to go?

[demolition]

The main reason that you cannot modify a PC drive into reading DSHD disks in Amigaformat is that it requires you to slow the RPM of the drive to 150 RPM instead of the default 300 RPM, which is not trivial. PC uses 300 RPM for both DD and HD formats.

[Mrs Beanbag]

How about reading PC HD disks on Amiga? Also how does the Amiga know there is a HD disk in the drive?

[robinsonb5]

Originally Posted by Mrs Beanbag

How about reading PC HD disks on Amiga?

Same thing - on the PC, HD disks deliver the datastream at twice the rate of DD disks. Paula can't cope with that, so Amiga HD drives halve the motor speed for HD disks, so the data rate remains the same.

[Mrs Beanbag]

hm, I wonder if it's possible to mod Paula, then, instead.

[robinsonb5]

Originally Posted by Mrs Beanbag

hm, I wonder if it's possible to mod Paula, then, instead.

I doubt it - the limitation is very much intrinsic to the Amiga's design: in order to shift twice as much data, Paula would need twice as many DMA slots, and would need to use a faster clock for disk transfers. (If Commodore had updated Paula to make use of the 64-bit fetch modes that allow the AGA screenmodes, then it'd be possible - sadly, they didn't.)

But I digress - the Alps drive is a fairly easy one to modify - I've done a few of those myself. Just need a steady hand, good light and either very good eyesight or a magnifying glass.

[Mrs Beanbag]

Originally Posted by robinsonb5

I doubt it - the limitation is very much intrinsic to the Amiga's design: in order to shift twice as much data, Paula would need twice as many DMA slots, and would need to use a faster clock for disk transfers. (If Commodore had updated Paula to make use of the 64-bit fetch modes that allow the AGA screenmodes, then it'd be possible - sadly, they didn't.)

Maybe we could buffer it somehow, read the data into a buffer and output it at half speed. The disk would do two complete revolutions, but the actual read would only happen on the first revolution... maybe...

But I digress - the Alps drive is a fairly easy one to modify - I've done a few of those myself. Just need a steady hand, good light and either very good eyesight or a magnifying glass.

It looked it, in fact most of the mods could be done off the drive, just on the cable. The only one that actually needs soldering is the ready signal, and optionally the HD detect if you can't be bothered putting tape on your HD disks. Unless I'm missing something?

Considering getting one with a black bezel and modding my case to let it poke through... I stripped the screw holes at the front last time I put it back together anyway

[robinsonb5]

Originally Posted by Mrs Beanbag

Maybe we could buffer it somehow, read the data into a buffer and output it at half speed. The disk would do two complete revolutions, but the actual read would only happen on the first revolution... maybe...

I think that's how Power Computing's external HD drive worked. (Kind of like the opposite of a scandoubler!)

It looked it, in fact most of the mods could be done off the drive, just on the cable. The only one that actually needs soldering is the ready signal, and optionally the HD detect if you can't be bothered putting tape on your HD disks. Unless I'm missing something?

You're probably right - but to be honest I found the idea of soldering onto the drive's circuit board less daunting (and certainly more fun!) than counting strands of ribbon cable, separating, cross-connecting and suchlike!

Considering getting one with a black bezel and modding my case to let it poke through... I stripped the screw holes at the front last time I put it back together anyway

That's a possibility, but if you want a less drastic intervention, what I did was remove the fascia and button from the drive, then shaped a new button out of polymorph, and Araldited it on.

Pretty? No. Serviceable? Yes. (That's a long-standing crack in the casework, BTW! )

[Retroplay]

I bought two new floppy drives from AmigaKit and I have some problems getting one of the drives to work properly.

One of them keeps giving me "DF0:????" on every disk I insert.
Disks that I know work and are perfectly fine on my other 1200 with original drive.

The other drive seems to work fine, although the demo "World of Commodore" gave me an error while loading (black screen with yellow text in bottom left corner), track load problems perhaps ?

Does anybody have any suggestions before I raise a support ticket at AmigaKit ?

[duga]

Originally Posted by Retroplay

I bought two new floppy drives from AmigaKit and I have some problems getting one of the drives to work properly.

One of them keeps giving me "DF0:????" on every disk I insert.
Disks that I know work and are perfectly fine on my other 1200 with original drive.

The other drive seems to work fine, although the demo "World of Commodore" gave me an error while loading (black screen with yellow text in bottom left corner), track load problems perhaps ?

Does anybody have any suggestions before I raise a support ticket at AmigaKit ?

Turn the cable connector 180 degrees at the floppy drive and see if that helps.

[robinsonb5]

Originally Posted by Retroplay

One of them keeps giving me "DF0:????" on every disk I insert.
Disks that I know work and are perfectly fine on my other 1200 with original drive.

What happens if you try and format a blank disk in this drive?