Twiggy Drives on eBay

[blusnowkitty]

https://www.ebay.com/itm/334481582186

Who needs a new car when you could buy a floppy drive?

[D.Finni]

I'd like to try connecting a Twiggy to the IWM in a Macintosh because I think the IWM can control them. What I don't know is to what extent, if any, the Twiggy drives in the Macintosh differed from Twiggy in the Lisa. Anyone here have any insight?

[sigma7]

I'd like to try connecting a Twiggy to the IWM in a Macintosh because I think the IWM can control them. What I don't know is to what extent, if any, the Twiggy drives in the Macintosh differed from Twiggy in the Lisa. Anyone here have any insight?

For a brief time I had a Macintosh Twiggy drive on my bench for repair...

IIRC:

• The Mac motherboard was the same as a 128K Mac (so yes, your IWM will work)
  
• The Digital Board for the Mac variant of the Twiggy drive is different from the Lisa variant. I think I have a picture... :-\
  
• The only difference in behaviour compared to the Sony seemed the polarity of one (or more?) of the sense signals was inverted, but I may be imagining it.
  

If I can find notes/pics I'll upload to the file section (... and I did)

[D.Finni]

The Digital Board for the Mac variant of the Twiggy drive is different from the Lisa variant. I think I have a picture... :-\

That's what I was getting at with my question. Also I see that the Lisa Twiggy had a 26-pin connector whereas the Mac ended up with a 20-pin connector.

[blusnowkitty]

The Digital Board for the Mac variant of the Twiggy drive is different from the Lisa variant. I think I have a picture... :-\

There's a picture over here: https://macgui.com/news/article.php?t=517

[sigma7]

Some more pics here:

https://www.flickr.com/photos/114907644@N04/albums/72177720300046948

[D.Finni]

Thanks you two for the photos and schematics. Now it looks like the root difference is that the 1983 Lisa didn't have an IWM, but the Mac did. So the Twiggy Drive needed a new interface board to talk to the IWM on the Mac.

Does this sound right to you guys?

[sigma7]

... the 1983 Lisa didn't have an IWM ...

The Floppy Disk interface circuit on the Lisa 1 I/O board is most of a WM before Integration. (I don't know but it might even be "The" WM that was the basis for the integrated circuit.)

Improvements were made once it was integrated into a single part (such as the Mac version needing 3 instead of 5 bitslip FFs), but the core functionality is the same.

You are probably wondering if an adapter between the Mac and a stock Lisa Twiggy digital board is simply a matter of the 20 & 26 pin connectors. It may be as simple as that, but my recollection is there was a hiccup (per my thought that some sense signal(s) were inverted). The hiccup(s) might be tolerable if you're just experimenting.

edit: A glance at the schematic shows the Mac variant of the digital board has a 7905 regulator to make -5V from -12. The Lisa variant doesn't have this as the Lisa PSU supplied -5V; so your adapter (probably) needs to provide -5V too.

[sigma7]

Lots of info about the IWM (and differences from the state machine made from discrete parts as in the Apple ][ and Lisa 1) to be had in the attachments to this post: https://lisalist2.com/lisalist1/0818.html

[claunia]

For that price I make a laser floppy dumper, geez, people are nuts.