lunes, octubre 04, 2004

Results of C64/128 diskette longevity experiments

Digno del Annals of Improbable Research:


---------- Forwarded message ----------
From: Paul
Date: Mon, 04 Oct 2004 09:47:00 -0000
Subject: [Classic Commodore] Results of C64/128 diskette longevity experiments
To: classiccommodore@yahoogroups.com



In three separate experiments (conducted at regular intervals), I
have determined the hypothetical longevity and general integrity of
data (both read and recorded) on the standard 5.25" floppy diskette.
Such diskettes are common to the Atari 400/800, Commodore 64/128,
Apple II/IIe and other 8-bit computers.

Here are the results of my experiements (conducted on 5.25" floppy
diskettes for the Commodore 64/128 line of microcomputers):

*************************************************************
Experiment One: Freezing diskette (Conducted in January 2003)
*************************************************************

Hypothesis: Frozen diskettes lose data, even if frozen overnight.

I froze a diskette overnight in a freezer, without the diskette
holder protecting the exposed mylar surface. I left the diskette
intact inside the disk jacket, though.

The disk received condensation on the exposed portion of the mylar
surface (of the diskette), and was extremely cold to the touch. I
noticed no physical alterations to the diskette, however (e.g. no
warping or physical damages; only coldness and condensation).

The disk drive booted the floppy disk directory without effort, and
the contents read without problem. Programs all loaded without
error.

Conclusion: Freezing a diskette overnight probably won't damage the
diskette enough to ruin diskette data integrity, but probably isn't
a good idea, anyway.

*************************************************************
Experiment Two: Overheating diskette (Conducted in June 2004)
*************************************************************

Hypothesis: Heating a diskette to even slightly above room
temperature is asking for data loss.

I overheated a diskette next to a space heater, without the diskette
holder
protecting the exposed mylar surface. The diskette melted a little
bit near the center, at which point I removed the diskette from the
space heater's range of heat. The diskette was heated for
approximately 10 seconds at a distance of 2-3" (inches) from the
space heater.

***DISCLAIMER***: *Do Not* attempt this experiment *at all* unless
you have _already_ safely practiced doing so!!! Heating any object
near a space heater is *VERY* dangerous and should *NOT* be
attempted by unexperienced person(s)!!

The reason(s) for testing the heat durability of a 5.25" diskette
were two-fold: One, I wanted to disprove the notion that a minimal
amount of excess heat can ruin a diskette's data integrity.
Secondly, I wanted to test the theory proposed that 5.25" HD (96
TPI) diskettes could still be formatted with a 1541/1571 disk drive
despite the small Tracks Per Inch (normal is 48 TPI on the Commodore
64/128 computers for a 5.25" diskette).

Conclusion: Heating a 96 TPI (HD) 5.25" diskette (or 48 TPI
diskette) to 95-115 degrees fahrenheit does not appear to affect
data integrity in any significant fashion, although outright
*burning* of the diskette *will* affect data integrity! The 96 TPI
diskette, once heated, formatted without error on both the 1541 and
1571 disk drives, but *could not* be reformatted once the diskette
cooled to room temperature (approximately 5 minutes time).
Additionally, the diskette had to be reheated to a high temperature
once again in order to reformat over the previous formatted contents.

********************************************************************
Experiment Three: Diskette burial for 554 days (March 2003-Oct 2004)
********************************************************************

Hypothesis: Burying a diskette for over a period of a year,
approximately 1.5 feet underground, will expose the diskette to
dirt, rain and other unsavory elements, even when contained within a
ZipLock(TM) plastic bag.

This experiment took exactly 554 days to complete...1 year, 6 months
and 7 days, to be exact. I buried a floppy diskette with (data on
both sides) in my parent's backyard at a depth of approximately 18
inches. I made sure that I protected the diskette as reasonably as
possible, including placing the diskette inside a paper disk jacket,
while also sealing the entire contents inside an enclosed ZipLock
plastic bag.

Conclusion: Even when sealed in a Ziplock plastic bag, and despite
being buried 18 inches underground, both the weight of the dirt atop
the diskette and the elements of water and wind severely warped the
diskette into a bowl-shaped wedge (think: bowl of soup wedged).

The poor diskette was unreadable as is; that is, without removing
the mylar internal diskette from the disk jacket itself and placing
it inside a new disk jacket (scrapped from a throw away blank
diskette I had no general use for). I noted the following damage to
the internal mylar diskette as I inserted it into the second disk
jacket:

A) Physical damage present near the center of the diskette, where
Track 18 was likely to reside.
B) Minor physical damage to the outer diskette, but mostly on the
left side where it had warped upward. Nearly identical damage was
evident on the right side, where the same warping was circularly
present.
C) Non-consequential smearing from dirt, visible just above the
(writable) track/sector area of the disk's mylar surface (left of
the main diskette ring hub).

The disk was inserted into the new diskette jacket and the jacket
itself was taped back shut via normal Scotch(TM) brand tape.

Conclusion: Because the diskette contained data on BOTH sides of the
diskette, I expected the back side to have less data loss than the
front side (due to warping/other damage). I was right. The results
of the data loss on the front side were as follows:

The disk directory read, but failed after only 7 programs had been
read (at least 40 programs were on the front side of the diskette in
late-March of 2003). This suggested serious damage to the middle of
the diskette, namely, Track 18. Not a good start.

I began loading the remaining programs one by one. Program 1, of 38
blocks, failed after only 0.5 blocks had been read. Since it was the
very first program on the diskette, this suggested it was written
very, very close to where the directory itself was written.

Program 2, a 3 block file, loaded 2 blocks out of 3 before it, too,
failed.

Program 3, a 7 block file, loaded fine, with 100% accuracy. However,
Line 23 of the program (read in Commodore 128 mode) was complete
gibberish, with weird commands like "CIRCLENEW TAN &STEPFOR" where
normal, regular BASIC statements would be. Line 24 was normal, as
was the remainder of the program. This suggested physical damage to
the mylar surface of the diskette.

Program 4, a 1 block file, loaded fine, with 100% accuracy, and
listed fine as well.

Program 5, a 63 block file, failed after only 1.5 blocks had been
read. This was very similar to how the first program faired.

Program 6, a 9 block file, loaded fine, with 100% accuracy, and
listed fine as well (with no errors). This surprised me greatly, as
a much smaller program did not.

Program 7, a 3 block file, loaded fine, with 100% accuracy, and
listed fine as well (with no errors).

I have not yet checked the remainder of the 1st side with Disk
Doctor 4.0, and have not read through each and every Track/Sector to
see how it looks in a diskette editor. However, Side 1 lost
approximately 500 blocks of data (roughly an 85-90% data loss). This
was the most severely warped (bowl) portion of the diskette, and
could only be read by the disk drive when I inserted the internal
mylar diskette into a new diskette jacket altogether.

The flip side, which was not damaged much at all, only contained
minor errors. The programs occupied a maxium of 61 *total* blocks on
the flip side of the diskette, leaving 603 blocks free. The
directory read without error, although Track 18, Sector 14 was not
readable. Because directory data was not on Track 18, Sector 14,
data loss on that particular T/S was not evident.

The programs (7 in all, out of 7 total) read as follows:

Program 1, a 3 block file, loaded 2 out of 3 blocks, but failed.
Listing the program only displayed most of it, with the last few
lines just pure gibberish.

Program 2, a backup of Program 1 (done intentionally), loaded all 3
blocks, and listed and ran fine.

Program 3, a sequential file of 3 blocks in length, was read through
the following "quickie" program:

5 PRINT"ENTER FILENAME";:INPUT A$
10 OPEN 2,8,2,"0:"+F$+",S,R"
15 GET#2,A$:PRINT A$;:IF ST<>64 THEN GOTO 15
20 CLOSE 2:END

The sequential file read most of the way through, but failed to read
anymore data halfway through the last 1/6th of the file itself.
Checking a backup of the same file (from another diskette), data
loss was between 2-3% of the file, with only the last few sentences
lost.

Program 4, a BASIC program of 18 blocks in length, loaded 12 of the
18 blocks before failure. Listing the program revealed gibberish
about halfway through the program.

Program 5, a BASIC program of 11 blocks in length, wouldn't even
load (gave a "?FILE NOT FOUND ERROR"; wouldn't even grace me with
a "LOADING PROGRAM"..."?READ ERROR" message).

Program 6, a BASIC program of 19 blocks in length, loaded with 100%
accuracy and without error. The program LISTed and was RUN without
any errors.

Conclusion: Burying a diskette even 18 inches below the ground for a
period exceeding 1 calendar year, even when protected in a ZipLock
(TM) sealed plastic bag, is generally *not* a good idea. Water (from
rain) and other elements warped the physical nature of the diskette,
as did the 18 inches of dirt laying atop the diskette (inside a
sealed ZipLock(TM) plastic bag). Even rescuing the internal mylar
floppy from the disk jacket and transfering it into a fresh disk
jacket failed to solve data loss. Physical damages to the diskette,
although minimal to the eye, were nevertheless responsible for a
total of at least 38 programs (out of 45 total) either loading only
65-70% of the way, failing altogether (0%-2% of the way) or loading
without error (only 5 loaded without error, and the largest program
of that variety was a mere 9 blocks in length).

Final Conclusion: Diskettes are surprisingly resistant to
temperature, but are very fragile to dirt, water and other
environmental factors. Even minor physical damages to the diskette
surfaces caused substantial diskette errors/loss. Errors noted (on
either side) were: #20, #21, #22, #23 and #27; no other diskette
errors were noted or found).

Sincerely,

Paul Allen Panks
dunric@yahoo.com

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