Atari/C64 flippy disks

[Rybags]

C64 disks use higher density but the default format only uses 35 tracks.

 

In theory you could have dual format on a side - give the Atari 28 tracks which = 63K, give the C= the remaining 12 which = just under 63K.

To achieve this the C= has to use tracks between 2-17 (Atari needs 1 for bootup). Those low tracks on 1541 have 21 * 256 byte sectors per track, it decreases twice as you move towards the centre with 3 zones with 19, 18, then 17 sectors/track.

C= needs track 18 for the directory and BAM.

 

In reality you'd probably want to leave a blank track seperating one machine's data from the other to be safe. But still, around 60K of media is sufficient to contain a program which doesn't need subsequent data loading, or a packed program with packed data which is accessed later.

Edited March 15, 2016 by Rybags

[sack-c0s]

They technically aren't multiformat disks are they?

 

I assumed each side was just formatted for the system in question and kept seperate

[Rybags]

In most cases I would think so.

 

Probably less expensive to just do mastering for a side at a time. Possibly mass duplication equipment could be different for FM vs GCR encoding?

[+CharlieChaplin]

They technically aren't multiformat disks are they?

 

I assumed each side was just formatted for the system in question and kept seperate

 

Yep,

 

flippies are not multiformat disks, since they have each version on one diskside (e.g. C64 on side A, A8 on side b).

 

But as said before, there exist multiformat disks that have both C64 and A8 version on the same diskside !

 

See these Mastertronic disks:

 

 

There is a yellow note in the middle of the label which reads: "This diskette contains both formats on the same side." (click the scans for a little higher 740x250 resolution)

Edited March 15, 2016 by CharlieChaplin

[+CharlieChaplin]

Mastertronic's Ninja

 

[a flippy disk...]

 

As you can see, my "Ninja" version is not a flippy, it`s a multi-format disk for A8 and C64 (on the same diskside)...

 

There is a multi-format version at ebay right now: http://www.ebay.de/itm/Vintage-Game-Ninja-For-the-Atari-or-Commodore-/121918857161?hash=item1c62ee1fc9:g:4HkAAOSwh6xTtthU

Edited March 15, 2016 by CharlieChaplin

[+Stephen]

 

As you can see, my "Ninja" version is not a flippy, it`s a multi-format disk for A8 and C64 (on the same diskside)...

 

There is a multi-format version at ebay right now: http://www.ebay.de/itm/Vintage-Game-Ninja-For-the-Atari-or-Commodore-/121918857161?hash=item1c62ee1fc9:g:4HkAAOSwh6xTtthU

That's awesome. How the heck did they do that?

[Rybags]

I think similar to how I described above. What I'd like to know is if they could do mastering in one hit or was a configuration change or loading into a different duplicator required (guessing here of course that they were mass duplicating using commercial equipment and not actual 8-bit machines and drives).

 

Pretty sure I had Ninja as a file and it's not all that big, probably under 30K.

[drrg]

 

Yep,

 

flippies are not multiformat disks, since they have each version on one diskside (e.g. C64 on side A, A8 on side b).

 

But as said before, there exist multiformat disks that have both C64 and A8 version on the same diskside !

 

See these Mastertronic disks:

 

multiformat_disk_ninja.jpg

multiformat_disk_speed_king.jpg

 

There is a yellow note in the middle of the label which reads: "This diskette contains both formats on the same side." (click the scans for a little higher 740x250 resolution)

 

I realize that the post I am responding to is 3 years old. I ran into the thread searching for something completely different but having to do with old 5.25 disks.

 

You are quite right, those disks had both Atari and C64 formats on the same side. I know this because I did them. For posterity or just plain trivia, here is the story as best as I can remember....

 

I was a brand new post-doc (nothing to do with EE or programming) and still quite poor. I had known some folks from Mastertronic through a local software company (Microprose) a year or so earlier. In the present cases, the guy who would have to make the flippies was keen on the idea of cutting production time in half - No flipping required..

 

I knew squat about Atari but was keen on the C64 1541 drives. I had added memory to the one that I had and it allowed you to do some unusual things. As it turned out, I needed that hack to make both formats on the same side. Or maybe it just motivated me to learn how to write whole tracks at particular locations. BTW: Adding memory was from an article that I read somewhere - it was not my creation. Bottom line was that I figured that there was no reason why I couldn't put both formats on the same side.

 

As I recall, I started with the Atari disk. I can't remember for sure, but I believe that I had to make sure they were on certain tracks only (low ones) and then I would selectively format and place C64 tracks on the diskette (again, this is where the memory expansion on the drive came in handy). There were some rules to follow, but it was pretty straightforward once I had figured it out. It was tested repeatedly and they worked great. They were very happy with it and, again as I recall, they paid me $100 each time I did this. Can't remember for sure, but I think I did this for 5-6 titles, including the two mentioned.

 

I just saw one of those disks tonight about an hour before reading this thread (I was actually looking for an alignment diskette). From my hand-written notes on the label, it was Speed King and it was dated 9/30/86 and the Atari tracks were on 1-13 and the C64 tracks were on 14-35. I also noted that track 37 was protected. I can't be sure, but I think it was something I came up with and I'm not sure it had anything to do with having both formats on the same drive, and, again as I recall, they didn't want any protection.

 

Wow, that was 33 years ago! You guys have some pretty good memories.

Edited April 14, 2019 by drrg

[ijor]

I realize that the post I am responding to is 3 years old. I ran into the thread searching for something completely different but having to do with old 5.25 disks.

You are quite right, those disks had both Atari and C64 formats on the same side. I know this because I did them. For posterity or just plain trivia, here is the story as best as I can remember....

...

Wow, that was 33 years ago! You guys have some pretty good memories.

Hi and welcome. It is always very nice and interesting to hear from those that were actually there. Thanks.