
Flipping your Disk (1981) - netgusto
https://www.atarimagazines.com/compute/issue10/036_1_FLIPPING_YOUR_DISK.php
======
NelsonMinar
There were custom tools for punching this hole in the exact right place, but
you could also just freehand it.
[https://content.spiceworksstatic.com/service.community/p/pos...](https://content.spiceworksstatic.com/service.community/p/post_images/0000129187/563b1bbd/attached_image/commod21.jpg)

The _really_ cool trick on an Apple ][ was eeking out an extra 14% storage by
modifying your drive to use 40 tracks instead of 35. Everything was designed
to work with 40 track disks but for some reason the standard Apple ][ disk
drive had a piece of metal physically preventing the disk arm from moving past
track 35. You could bend / cut that out of the way and get 40 tracks. Even
more if you hacked your software and trusted the disk media beyond track 40.
But that was dodgy, up to track 40 was mostly safe. Except it broke a few copy
protection schemes that would slam the disk arm all the way to the outside and
expect that to be track 35.

~~~
berbec
I used a similar trick to get 1.68MB on a 1.44MB floppy. the extra 240KB
really made a big difference in boot disks.

0:
[https://en.wikipedia.org/wiki/Distribution_Media_Format](https://en.wikipedia.org/wiki/Distribution_Media_Format)

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dhosek
I used to do this all the time back in the day. I also used to buy floppies in
bulk from some mail order catalog and re-sell them at a profit from my high
school locker.

~~~
legohead
how many kids had computers? when I was in HS I was using 3.5" floppy and
there were only a handful of us that had computers...

~~~
kbutler
They didn't necessarily have computers, but they used computers.

~~~
dhosek
Only a handful had computers, but there were enough who used the school
computers to make it worthwhile. I didn't own my own computer until I was out
of college.

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xrd
I saw the author's name (MG Sieg) and thought it was MG Siegler (TechCrunch,
now at Google Ventures:
[https://en.wikipedia.org/wiki/M._G._Siegler](https://en.wikipedia.org/wiki/M._G._Siegler)).
MG Siegler was born just a few months after this article was published in
1981, so unless he was publishing in-utero, it was a different person.

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forinti
And you can use a 3,5" floppy as single/double density if you cover the hole
on the left (opposite the write-protection hole).

It's not supposed to work, but I've had a floppy like this for years and it
reads fine.

~~~
wazoox
Using a HD 3.5" floppy as a DD one is fine, however doing the reverse won't
end well :)

~~~
LeoPanthera
It's actually not fine. I don't understand the chemistry but using an HD disk
in a DD drive will appear to work, but the data will not be written "strongly"
and will "fade" after a short time, becoming unreadable.

~~~
tomatocracy
It’s coercivity of the magnetic medium. HD disks have higher coercivity than
DD which means higher write current is needed to put phase transitions down on
the magnetic medium when recording. There are also some differences with track
widths which complicates things further if you try to reformat from HD to DD
without first degaussing.

For 3.5” disks the difference is small enough that you only tend to run into
problems if you format a disk as HD in an HD drive then try to reformat and
reuse it in a DD drive as DD without degaussing first (because the DD drive
won’t be able to fully remove traces of the previous HD signal).

For 5.25” though the difference in coercivity is quite a lot bigger and even
using freshly degaussed HD discs in a DD/SD drive will very likely lead to
problems quite quickly.

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js2
Ah the memories. It turns out that Elephants do forget, especially on the
second side.

[https://en.wikipedia.org/wiki/Elephant_Memory_Systems](https://en.wikipedia.org/wiki/Elephant_Memory_Systems)

[http://blog.modernmechanix.com/remember-elephant-memory-
syst...](http://blog.modernmechanix.com/remember-elephant-memory-systems-
never-forgets/)

[https://www.youtube.com/watch?v=TDPbBO8jUA4](https://www.youtube.com/watch?v=TDPbBO8jUA4)

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bakoo
Fond memories! Eventually did the same on my C64 floppies, but only after
having destroyed quite a few disks using my mom's blunt, giant scissors.

Used a soldering iron on my 3.5" disks, with a scalpel to take care of the
excess plastic. Can't remember why I didn't use a drill, but I suspect
drilling ran a bigger risk of particles getting inside.

~~~
llsf
I did drilling :) worked fine if I recall correctly. You had to spin fast, so
it does not crack open the case. Memories indeed...

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StanislavPetrov
Punching a hold also made the 5.25 disk read/write instead of read only. Games
and other software would often come with a "master disk" with no hole punched,
and direct you to make a duplicate (or set of duplicates) that you would play
off and save to.

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Wowfunhappy
Why weren't floppy disks sold this way to begin with? Some sort of economy of
scale type thing?

~~~
dboreham
When you flip the floppy over the media rotates the other way. Supposedly the
inside of the jacket had a fabric coating who's purpose was to catch fragments
of media falling off during use. If you spin the media the other way those
fragments come back off and gunge up the head. Or so the story goes.

Also of course there were real double-sided drives that used both sides of the
media (with two heads). Vendors expected users to use those and pay extra.

Source: punched many a hole in Pet floppies back in the day.

~~~
joezydeco
There was indeed a fabric coating in most floppies, but in my experience
taking them apart I never found any material that looked directional.

[https://upload.wikimedia.org/wikipedia/commons/thumb/2/21/8-...](https://upload.wikimedia.org/wikipedia/commons/thumb/2/21/8-inch_floppy_disk_-
_IZOT%2C_Bulgaria_-_inside.jpg/1280px-8-inch_floppy_disk_-_IZOT%2C_Bulgaria_-
_inside.jpg?1569886136207)

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geephroh
Pro tip: Don't try to punch an extra timing hole.

~~~
simonblack
You can, _if_ you are careful. The method is to indicate the position of the
new index hole on both sides of the envelope with your template, and carefully
insert the 'anvil' part of a hole punch through the large centre hole and
between the active magnetic disk and the envelope. Punch the index hole on one
side of the envelope then repeat the performance with the other side of the
envelope.

I found that it was very rare for my 'flippies' to be unusable in my Z80 CP/M
computer of the time.

Of course when we were able to afford those new-fangled double-sided drives,
the whole incentive to make 'flippies' disappeared overnight.

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my_left_bit
It was easy enough to replace the notch-reading-switch with a toggle switch on
the front of the drive, and optionally wire an LED in series. Then you could
write-enable without a notch, and write-protect despite one. Like the
mainframe disk drives!

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simmons
Hmm, using a hole puncher is a pretty clever idea. If I had thought of that,
instead of crudely sawing off a notch with scissors, maybe my success rate
would have been higher. ;)

You can also punch holes in 3.5-inch double-density disks to attempt to turn
them into high-density disks. :)

~~~
colanderman
There actually existed hole punchers specifically for floppy disks. You lined
them up to the corner of the floppy, and they'd punch a square hole at the
proper location.

~~~
myself248
I recently found a large stash of these and gave them away at VCFMW. Then I
found more in my basement...

~~~
benj111
I'll trade you one for my mouse roller cleaner, I'll even chuck in a mouse
mat, and an AOL disc.

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zaat
Good old Wikipedia have some more info, filed under flippy disk

[https://en.wikipedia.org/wiki/Floppy_disk_variants#Flippy_di...](https://en.wikipedia.org/wiki/Floppy_disk_variants#Flippy_disks)

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HenryBemis
NOW you tell me???? It would be nice to know in the 80s when I had my Amstrad
PC 1512!

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josteink
If this is news, I’m officially old.

Good times.

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ninju
What about the fact the timing hole was on the wrong side? Wouldn't that have
affected the hole reader since it would never be able to read through the disk
OR was there a reader on the other side

~~~
AndrewStephens
I don't know about every machine from that era but neither the C64 or the
AppleII used the timing hole, relying on special signals on each track to
identify the start of sectors.

~~~
jhallenworld
Atari didn't need it either. The 1771 (or 2793 I think) floppy controller chip
(a standard chip for IBM formatted floppies) does need the index pulse for the
write track command for formatting. But the signal is just connected to a GPIO
(I think on the 1050 drive this was fed by a timer).

This saves money, eliminating the need for the index pulse LED and photo
transistor.

Reads never need the index pulse on soft sector floppies. Each sector has a
header with the sector number and an "address mark" (a unique data pattern)
used to detect the beginning of each sector and track.

Hmm, except the index pulse may have been used for a timeout if I remember
correctly.

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newobj
Didn't even need a notcher. I just used a pair of scissors.

~~~
acomjean
I did it with an exacto knife. Some of that 5.25 inch floppy material was a
little tough.

In some magazines they advertised a special hole punch with some alignment
guides to do this, but it seemed expensive.

Most boxes of disks included stickers to recover the existing notch to write
protect your disks too...

~~~
aperrien
When I was a kid, I made an alignment tool out of cardboard, and later plastic
from old whipped cream containers.

~~~
ansible
Yup, I made my alignment tool from a floppy disk sleeve. Made it easy to mark
the location with a pencil, and then go in with the hole-punch to get it
exactly right.

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KibbutzDalia
I never ever had a problem on the other side.

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pravda
There should be a (1981) in the title.

~~~
kazinator
"Make your 5.25" floppy double sided by punching a notch" hardly needs to be
qualified with (1981).

~~~
cies
Maybe some younger views will be less shocked by not knowing what's a floppy.

~~~
davidw
The joke I've seen: "someone made a 3d printing of a save icon!"

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aerophilic
Add 1981 =)

