CF2 mass disc testing results

Started by Velociraptor, 02:06, 16 December 21

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Velociraptor

Over the past 30 months I have bought as many 3" CF2 discs from eBay as possible. I've paid £2.50 at most for each of them and for some a fair bit less.


I have spend the past few days testing all of them and I hope my findings are of some help or at least some interest.


Total : 258 discs


Testing Method


Using Multi Mark on my CPC664 with a freshly serviced drive - new belt and greased.


Multi Mark has this neat feature  where if it finds bad blocks it will allocate them to a dummy file thus "using" them on the disc. This means that the disc can then be used to store other things. My intention is to use them to store budget tape games to save on loading times from tape. I'm concerned that if the disc already has some faults then it may develop more and fail again.


Each commercial disc was tested with a verify. if any errors were found in blocks allocated to files on a data format disc or at all on a vendor format then the disc would be deemed corrupt and a format/verify would be tried just like a non-commercial disc. I was aware that some may have this as copy protection but sadly all of the game discs I had loose had lots of errors anyway.


Each non-commercial disc was tested with a format/verify sequence. If there was only 1KB of errors I would repeat the format/verify up to 2 more times. I do not know if this will result in problems for me in future, but a significant number of discs would be excluded otherwise.


A 3" head cleaning disc with IPA was used after 2 faulty discs in a row. Just in case there was any possibility of dirty heads.


Results explained


A disc that passed simply means it has no bad blocks on either side.

A disc that partially works has some bad sectors.


A disc that fails either has a mechanical problem with the metal mechanism - in which case it was rejected without testing. Or the catalogue fails - this as far as I'm aware renders it useless. Or it had such a significant amount of bad blocks that I would consider it contaminated/beyond repair/falling apart.


Types of discs and results

All of the discs I have are listed on the wiki already.

From the pictures [size=78%]CF2 Compact Floppy Disc - CPCWiki[/size] I had...


Amsoft, Tatung, Maxell, Amsoft CF2DD (1 single, Noname, Copy Amsoft (1 single), Panasonic. Possibly others that aren't easy to tell apart.


All of my discs were obtained from eBay. No large batches were bought over perhaps 30 discs from any one source.


I agree with the placement of the discs on that page. Amsoft, Tatung, Maxell performed best. Panasonic I only had a few of but they weren't as good. Noname (with the circle design on the plastic housing) were junk and only 1 single disc passed. The copy Amsoft (which is like an Amsoft but the detailing on the plastic housing isn't right and it is more shiny) passed.


I also had a number of discs from the 8000 PCW magazine and they all but one failed.


Discs that had been used for games - commerical or "public domain" 🏴‍☠️ fared considerably others.
Discs that had been used for business (often PCW type thing) fared considerably better than others.
Discs that had been used for home accounts/etc fared in the middle.


Discs that had been used on a Spectrum mostly failed. Only one that was clearly ex-Spectrum passed. There were maybe around 15.


Discs with dirty labels failed much, much more than other discs.
Discs that were stored in cardboard sleeves may be slightly better but it's difficult to say.
Discs in plastic clamshells fared much, much better than other discs.


So it's clear that how well the discs have been looked after has an impact. Presumably at one end businesses take great care of the discs and store them sensibly, and the other end a 12 year old kid chucks them about the place.


However the overwhelmingly best indicator of disc health is the metal shutter. If the metal shutter is beautifully clean and shiny then the disc almost always passed.
If the metal shutter had any smears on it, especially if it looked like water had dried from it then the disc had errors. The more signs of this the worse the disc got.


I conclude from this with a great deal of confidence that discs stored in lofts (may be called an attic elsewhere) or even worse stored in a garage or shed are doomed. The signs on the metal shutter are that condensation has formed and been drawn to where the shutter and plastic meet and contaminated the disc surface.


So I would urge anyone buying discs to look at the metal shutters if possible.


Disc test results


Total 258 | 152 59% fully working | 68 26% partially working | 38 15% dead


258 total discs
152 working discs 59%
68 partially discs 26%
38 dead discs 15%

GeoffB17

Hello,

Thanks for the 'survey'.

Yes, I'd suggest that the most important thing is the 'how the disk has been cared for' factor.

One thing.   May not be worth the trouble?

For any disk that has failed, I would try a substantial magnet and seriously wipe the disk clean.   Then try again.   Sometimes a disk can fail due to spurious data just outside the track width you've just written.

Geoff

ralferoo

I'm not sure if Amstrad disks actually use the "index hole" (I'm showing my age here, no idea what it's called on disks smaller than 5.25") but if it's just based on sync markers on the disk, then reformatting the disk might move sectors around and leave a tiny defect in the inter-sector gap when it might previously have been in a sector. I believe once the disk is formatted, the 765 only uses the markers on disk to read/write in the appropriate place.


Even if the index hole is used, you could try formatting an extra long track, knowing that the early sectors will be overwritten as the disk goes past a second time, but the sectors will end up coming a few bytes earlier or later depending on the speed of the motor, so if you do this long enough, you might manage to avoid any bad spots.


That said, you should probably consider all physical floppies of that age to be "at risk" as the oxide layer could easily degrade further without warning. So make sure you have backups of everything and only use the physical disks if you really want the sensation of putting an actual disk into the drive.

Velociraptor

Yes I had considered properly wiping the discs to see what would change.


It might be worth it for the minor fail discs. For the discs that have major fails on them, most of them have some kind of physical clue as to why they have failed - they are dirty, tatty, or there is some kind of marking on the metal shutter. So I don't think it's worth bringing those back.


But for the minor ones then perhaps a wipe with a magnet and a reformat might change things.


And "at risk" is what I'm thinking. Especially while I have a large number of functional discs do I really want to try to get "at risk" discs working again? For my purposes the partially working discs can be used for games I already have on tape just for convenience, so that if they do degrade further I'm not losing anything.




GeoffB17

Yes, I understand your points, and in the end it's a matter of what's worth the trouble.

I started using floppy disks 1983.   5.25" dd types.   I started using disks with my PCW in 1985.   Both 3" disks, and soon after 5.25" again.   99.?% of my floppy disks still work fine, and seem totally reliable, although I do have occasional problems with HD types.   But then I have ALWAYS treated my disks with respect, and looked after them.

As far as I know, the index hole (just a single hole on soft sector disks) is used, merely to align the start point of the formatting of each track.   It plays no part in the actual format (data) that is written to the disk to define the indiv tracks/sectors.

Geoff

ComSoft6128

FYI


Dixons also sold their own 3" discs (unbranded Maxell?) in boxes of ten for a few years. I found some of the labels recently which reminded me.

zhulien

I guess not bad longevity considering the type of media, and they likely weren't created to be working in 30+ years time also.  I think in some way it is a testament to how reasonably well they are made.

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