Floppy drive selector board

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Floppy drive selector board

Post by spags » Mon Apr 25, 2016 2:24 pm

This isn't really a feature request but I have this crazy idea of an add-on board (actually, more like a controller board) for Kryoflux but have neither the time, resources or knowledge to implement it. I suspect it may be quite costly as well, but I'm documenting it here for anyone to pursue should they feel so inclined.

I would guess that most Kryoflux owners have several drives in their collection. Whenever I find the need to use my Kryoflux, I pull out the bunch of drives I think I might need to use, connect everything up and use. Afterwards, I then disconnect it all and pack it away. I take care with plugging in and removing the floppy cable, but there will only be so many times that it can be used in this fashion before it starts failing.

My idea was to connect all of my drives to the Kryoflux and never need to disconnect them again. I wondered if there was such a thing as a floppy drive selector (like the old parallel printer selector boxes). I don't think there is and it would need to be a magical board where you feed it the 34-pin floppy cable with the 4-pin floppy power, and then it fans both of these to all the drives you have connected to it.

I realised that it wasn't going to be easy. There would be a set of drive selector buttons (so that you could pick which drive to use), but this board would need to be smart to make sure that it connects and disconnects the selected drive in the correct manner. It would need to have an onboard micro controller to handle this, as well as the Kryoflux USB connect/disconnect as well.

To control the connection for a single drive, this board would need to be able to control 17 (maybe 18 - don't know why pin 33 in the KF circuit diagram is not ground) data lines and 4 power lines for each drive (of course, with both sizes of connectors as well). Possibly the same types of buffer drivers could be used as found on the Kryoflux itself, but the power lines would probably need to be controlled by 2A relays. The 17/16 ground pins would be constantly connected between the board and the drives, so only the remaining 17/18 + 4 would need controlling. No ridiculous power supply would be required because only the board itself and the selected drive would be actively powered.

Such a board would be intended to operate the Kryoflux in single-drive mode. It would probably also be designed to switch up to 8 devices (for simplicity sake, say 1 Kryoflux board and 7 drives). If designed correctly, it could have its own type of daughter boards that allows for daisy chaining of those 7 drives to another set of 8 drives - one board could switch up to 57 devices. This would allow for advanced users or institutions to modularly upgrade their board to cater for the number of drives in their collection.

Disadvantages/Possible problems:
Noise - the use of the tri-state buffers should reduce this but with such a complex setup, noise seems likely especially towards the most distant drives in the topology.
Size/cost - the base board would probably be a little deeper than the Kryoflux and definitely much wider (one drive needs 3 buffers, the 34-pin connector, 2 or 4 relays and 2 different sizes power connectors - multiply all that by seven) - plus a bus to handle all that, then circuitry for the micro controller and selector buttons. The daughter boards would be slightly smaller, but at least since they would be the same they would be cheaper to produce in quantity.

Enclosures - home users could mount almost everything in a full-size ATX tower, pros could make huge dedicated drive enclosures/walls - one mains power in and one USB in.
Set and forget - no need to worry about connecting/disconnecting in the correct order.
Cost - while this would probably rival the cost of a Kryoflux itself, it means only one Kryoflux is required (as opposed to having multiple Kryoflux boards embedded in multiple different enclosures).
Double up - while it is intended for the Kryoflux to be used in single-drive mode, it may be possible to still use two drives per cable.

I'm sure there are things I have missed or show-stoppers, but that is the general idea.

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Re: Floppy drive selector board

Post by SomeGuy » Mon Apr 25, 2016 5:42 pm

You are over thinking it a bit. The Kryoflux already supports up to two floppy drives connected via a "standard" IBM PC twisted floppy cable.

Because the Kryoflux is generally treated as an archival tool for games, rather than an interoperability tool, I suspect many, including the developers, are happy with simply a 1.44mb 3.5" drive and a 1.2mb 5.25" drive. And because there are few copy protected titles on 3.5", even just a 1.2mb may be enough for most.

Although the way I use mine, it would be handy to have a 1.44mb 3.5, 1.2mb 5.25" and 360k 5.25" drive, all mounted in a mini ITX case like this: http://www.newegg.com/Product/Product.a ... 6811147131

That way the only time I would have to reconfigure anything is when I need to hook up my 8" drive. I'm not aware of any current enclosures that could fit that. :)

At any rate, all you would need to control are the drive select lines. The original Shugart floppy interface actually supports up to four floppy drives on one flat cable. (IBM gimped that) The Kryoflux hardware might technically be able to operate in that mode, but as far as I know the software does not support that. And most 3.5" drives are not designed to operate in that mode.

You would not need to switch power, just plug all of the drives in to their own power supply.

Beyond that, all you would need is a physical switch for the drive select or perhaps a couple of simple TTL logic chips if you wanted to do some fancy trickery.

On a Kryoflux, when a drive type is changed the only thing that needs to be reconfigured is the maximum number of tracks. So using a physical switch to switch between a 1.44mb and 1.2mb drive would be easiest.

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Re: Floppy drive selector board

Post by ChrisCwmbran » Mon Apr 25, 2016 9:35 pm

I like this idea. Sometimes I do actually use my KryoFlux to write an image to media for a disk I need.

I have four drives I connect though: 5.25" 40 track, 5.25" 80 track, 5.25" HD and 3.5" HD.

I'd buy something along these lines.

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Re: Floppy drive selector board

Post by spags » Tue Apr 26, 2016 11:46 pm

@SomeGuy You are too kind for suggesting I was only "over thinking it a bit".

I was aware that the original Shugart interface supported four drives but it was my understanding that the Kryoflux only supported the IBM PC interface (hence the two-drive jumper on the board).

In some ways I can understand your statement that only the Drive Select line needs switching. Thinking about a standard twist cable, both drives will be receiving the same signals (the cable wires don't magically separate with the corresponding DS signals), so obviously that scheme works. However in other ways that would seem to be a potential source of noise (or signal attenuation). Is that why single-drive mode is suggested in the Kryoflux quick start guide?

In that case, why is the Kryoflux using tri-state buffer drivers on all but the ground lines? Okay - obviously there is the concern that the micro controller may not be able to sink/source the current, but why not just use standard buffer drivers (without tri-state)? Looking at the Kryoflux circuit diagram, it certainly seems to use the tri-state ability to disconnect those lines.

I'm also unsure about the suggestion that the power lines wouldn't need switching. Is that because you are suggesting virtually all of the signal and ground lines would already be connected together anyway (and therefore no concern about disparate grounds).

Personally, I probably have a mix of about 8 different drives (3.5 and 5.25), which I find give varying levels of performance over different disks (although I have a few favourites). I find it somewhat surprising that you can have a single dedicated drive for a given medium and just rely on that single drive to get "the" dump.

Based on the comments here so far, it sounds like the daughter board idea would be overkill anyway.

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Re: Floppy drive selector board

Post by Pheonix » Fri Jun 22, 2018 4:45 pm

Actually, you could connect up to 2 3.5" floppies as well as 2 5.25" drives. Most 5.25" drives have a jumper to select drive 1-4. Or 0-3 depending on the drive, but it amounts to the same thing, just add or subtract 1 depending on your viewpoint. The trouble with most 3.5" is that the drive is hardwired as drive 2 (no jumpers, though there are exceptions.) That is why the standard floppy cable later came with a twist (originally it didn't have one, the 5.25" drive was expected to be the A: drive or drive 1.) The twist reverses the drive select lines so that the drive becomes "jumpered" as drive 1.

The answer here, is to have one 3.5" drive before the twist & one after, so that you have 3.5" drives as drive 1 & 2. Then just jumper your other drives as 3 & 4 and keep them before the twist. The only problem that arises now is that 3.5" drives also have termination hardwired in as well. Though, most of the time, this won't make a difference.

All you would need is a cable with 4 connectors. Would either have to crimp on the IDC connectors yourself or have the cable custom made.

So, the next question is... Does the the Kryoflux even have the drive select lines for 3 & 4 even connected to anything. If so, it seems only a firmware & software update would be all that's needed to enable setting for up to 4 drives. 1 8", 1 5.25" 40 track, 1 5.25" 80 track, and 1 3.5" 80 track. Operationally, an 80 track DD drive will have the same compatibility issues as the 80 track HD drive when writing disks that are to be used in a 40 track drive. They both have the 96tpi instead of 48tpi issues. So there really isn't a need to use both an 80 track DD drive & an HD drive. What you need, for compatible writes (reads have no problem if you have a good HD drive,) is a 40 track drive. That's what I'm looking to get next. A 40 track drive so I know that there's a better chance disks I write will be read by my original HW.

The only reason to have a 720k 3.5" drive, that I can determine, is to force DD mode for HD disks. Which is never advisable, and can be accomplished (usually much cheaper,) with some masking tape. If the EHD drives (2.88 MB+,) have the same problem as the 2.4 MB 5.25" drives, then you would need a 720k or 1.44MB drive to go with it for compatibility issues. But, I'm told, though I haven't researched it myself, yet, that the 2.88 drives didn't have this problem.

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Re: Floppy drive selector board

Post by mr.vince » Mon Jun 25, 2018 8:59 pm

KryoFlux supports two drives only, and if someone approaches us, we _recommend_ only one device at at time. This is "ancient" technology; the more devices there are, the higher the chance that - for whatever reason - certain devices will cause static/noise on the bus. The bus works as an open collector by supplying TTL level (+5V) voltage with a low current (something between 1kOhm and 10kOhm). A logical 1 is when the bus gets pulled to 0V (with a "short circuit"). The more drives there are, the more drives will drain this voltage. A modified logical 0 (originally +5V) due to a very old drive with a high "standby" drain might e.g. lower the current or the voltage; this might lead to modified timings (when the signal is pulled to 0 or goes back up to +5V).

And no, most pro users don't use it for games, but for general archival. See: https://kryoflux.com/?page=kf_refcustomers

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Re: Floppy drive selector board

Post by martysmarty » Thu Mar 07, 2019 2:10 pm

Jumping in on this older thread. mr.vince: Is there any way (perhaps not documented) to connect more than 1 kryoflux board to a PC, and specify to dtc which board should be used? (I'm not even talking about using them both at the same time. 1 at a time, but specify which one.

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Re: Floppy drive selector board

Post by ZrX » Sat Mar 09, 2019 4:55 pm

It is possible by modifying and installing two drivers (requiring driver signing to be disabled from Windows 8 and up) and modifying DTC.exe for the second board.

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Re: Floppy drive selector board

Post by martysmarty » Sun Mar 10, 2019 5:31 pm

How about Linux? I see multiple devices when connected to one machine. Not sure one could change the linux binary though

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Re: Floppy drive selector board

Post by brightcaster » Sun Mar 10, 2019 8:12 pm

If you don't want to use both devices at the same time and simply want to switch between devices (without changing the cables) instead, you can turn the corresponding usb-port on and off:

http://migueleonardortiz.com.ar/linux/l ... linux/1645


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