... I didn't see Basic Plus listed.
I have some kind of Basic on two Twiggies, but one of the disks has a couple of bad sectors in the disk directory. I enlisted the help of Claunia, the
Aaru (formerly DiskImageChef) developer to fix those, but I haven't yet tried to install it to check that it was 100% successful.
How many Twiggies is your variety of Basic?
So the question is what am I looking at here?
- Was a guide ever created for this process?
- Are there any potential snafus that can happen in this process?
- What are the concerns 15 years later?
There is no guide at this time -- please feel free to ask all the questions.
There are very few people that have done this (or few have reported doing so), and so there is not much to compile from; I'd say all the details haven't really been worked out. Since you're just starting the adventure, making some notes/taking pictures of anything non-obvious along the way might help someone else.
My personal experience is that the pre-BLU reports of old Twiggy media easily shedding into oblivion isn't common. Oxide does come off and contaminate the heads so they stop working until cleaned, but I found the media has remained somewhat readable.
Some old media has high friction jackets that keep the disk from turning at the desired speed (which is solved by putting the donut in a more modern jacket).
I recently received a batch of Twiggies to archive, and found two things made a big difference for few disks/tracks for this batch; the upper jacket pad and spoofing the track 0 position sensor. I'll post about those separately.
However, my experience is not necessarily indicative for a general case; Different storage conditions affect the media, and I quite probably naturally avoid working with disks that clog the heads -- my Twiggy usage is different from most.
General advice that I can think of at the moment....
Make sure your archiving setup is working well before trying any rare or valuable Twiggies. That includes:
- serial interface and xmodem transfers are working: There are reports of transfers failing at the last block (on some varieties of Unix using some USB-Serial adapters), so make sure transfers run to completion.
- Your twiggy drives can format, read, and write successfully. Although you only "need" one drive, it seems they are all a little different and so more working drives makes it possible to archive more sectors of a difficult to read disk.
- You have a good way to clean the heads, ideally with a way to verify they are clean or need cleaning.
I do not have a good way to check the rear/upper head short of disassembling the drive. I'm working on a fixture to position a low cost USB endoscope camera for this purpose, but it looks like I won't have a good solution for a while.
I am slowly working on a revision to BLU that I hope will help archive difficult to read Twiggy disks... anyone interested in alpha testing please DM.