Greaseweazle v4 with dual QL 3.5" drives - possible?

[Sparrowhawk]

So, apparently a long time ago I was a young lad. At university I had my QL, and then an Amiga on which I wrote my dissertation, as did at least one of my flatmates. Anyway, after uni I sold the Amiga (kept the QL of course!)

Fast forward to the present day, and after chatting with said flatmate, we wondered (not for the first time) what we actually wrote back in the day, our memories oddly enough not prioritising the contents of our uni work. I still have the disks, but no computer, and frankly I've never been willing to pay £200+ for an Amiga just to find out.

And then yesterday I stumbled a thing called the GreaseWeazle (v4) - (https://mattfife.com/?p=7234) (software info: https://github.com/keirf/greaseweazle)

At only £33 on eBay, I ordered one with a view to using it with my twin Power Computing QL drives (3.5")

And then, being the hardware numpty that I am, I suddenly realised that they may not be compatible. I believe the QL drives use the Shugart interface (they work with my SGC and SQB so... yes?). However, as they have a dual floppy ribbon with single connector, can I use them with the greaseweazle? Would somebody who understands the world of disk interfaces be kind enough to look at the pages above and let me know whether I can safely plug the drives' combined end connector into the interface without blowing up one (or both)?

Thank you

PS - this may be of interest for people doing software preservation generally?

[Sparrowhawk]

I found this on the setup pages. I don't fully understand it but it suggests that maybe I shouldn't use the twin drives (or is it OK as I have 3.5" drives)?

Drive terminations

The standard floppy bus is open collector with termination (pull-up resistors) at the far receiving end.

The terminations on older 5.25- and 8-inch drives can be as strong as 150 ohms. It is also important that only one drive in a bussed setup has 150-ohm terminations: Greaseweazle V4 cannot drive into multiple strong pull-ups in parallel.

The strong termination in older drives is usually optional because only the last drive on a ribbon cable is expected to terminate. The terminating resistors on intermediate drives are traditionally either disabled by a jumper, or removed entirely. This correctly terminates the signal lines and also prevents overloading the drive controller's outputs with excessive pull-up current. However, if termination is missing entirely then the drive input signals will float (usually at around 2 volts) with unpredictable results!

If using 3.5-inch and 3-inch drives, this is not a concern. Their terminations are weaker and cannot be disabled.
If using a 5.25- or 8-inch drive on its own, make sure that the termination resistors are present and enabled.
If using a 5.25- or 8-inch drive in a multi-drive setup, you probably do not need the termination resistors.

Note that an unterminated setup will work with other flux boards such as Kryoflux and Supercard Pro, which actively drive their outputs both high and low. Greaseweazle by contrast has standard open-collector outputs which rely on termination resistors to pull signals high.

[Ruptor]

You say

I believe the QL drives use the Shugart interface (they work with my SGC and SQB so... yes?). However, as they have a dual floppy ribbon with single connector, can I use them with the greaseweazle?

and greaseweazle says "Floppy drive – any 5.25″, 3.5″ or 8″ floppy that uses the Shugart interface"
So are you just querying the cable where they say a suitable one is here.
http://www.cablesonline.com/36unflopdriv.html
The odd thing with PC dual disk cables is they have cut and twist in the ribbon that you can just see in the cable picture. If you look at the 5.25" drive on the greaseweazle site the cable has the ribbon twist so is a standard PC cable.

[Ruptor]

I found this on the setup pages. I don't fully understand it but it suggests that maybe I shouldn't use the twin drives (or is it OK as I have 3.5" drives)?

If using 3.5-inch and 3-inch drives, this is not a concern. Their terminations are weaker and cannot be disabled.

The weak terminations means two 3.5" drives isn't a problem.

[Chr$]

I have a greaseweasle v4 and I used a QL cable with it (think it was a Miracle systems drive cable) because it's 'straight through' without the twist that PC cables have, so was a convenient length. I only used it with one drive though (that's all you need of course) and that was just any-old PC drive that was gathering dust as it doesn't matter if it's a 720k or 1.44m drive. The QL drives are set to DS0 as opposed to PC drives always being DS1 but that doesn't really matter either as you can specify DS0/DS1 in the greaseweasle program.... I recommend a GUI as it's easier to tick boxes on screen instead of remembering parameters.

I used mine to dump some Spectrum +3 disks (in a 3" drive obviously, but that was a little more complicated due to the 3" drive not having the same type of connector as the ubiquitous 3.5" drives).

[Sparrowhawk]

Thanks for the replies. Will try it asap.

[Derek_Stewart]

Hi,

Try looking on YouTube gor Greaseweazle info:

https://www.youtube.com/watch?v=zN9PL29RT9M

https://www.youtube.com/watch?v=xQcuRNcjtXg

The video describe read/wtite of Amiga Disks

For PC formatted disks use QPC2 v5, reads the disk and will copy to a QL floppy disk

[Sparrowhawk]

Hi Derek,

Yes, the second link (MikeyGRetro) is the video I stumbled upon yesterday (via Mastodon) which got me going on this. the CLI interface looks simple enough. I was just checking that I would not damage my drives or greaseweazle as all the videos seems to be using a single drive unit.

[Derek_Stewart]

Hi,

Just set:

Drive 1 to DS0
Drive 2 to DS1

You can not damage the drives, just use straight cables

[Sparrowhawk]

Thanks Derek