Format 1.4mb disk for 800k

[RickNel]

This topic is probably an old chestnut buried somewhere, but I couldn't find a thread about it on this forum. :I

I need to make a number of 800k disks from images for my 512ke, but I don't have any 800k-specified disks.

I can use the superdrive and software in my IIsi, or the 800k drive in a Plus, to make iiniitalise and burn floppies reported as successful. If the right-hand notch on a 1.4mb floppy is covered over, the drive sees it as non-HD double sided. I've read various comments on different forums about how reliable this can be.

What is the experience of members here with using 1.4mb disks as Mac 800k disks?

What other way to source disks suitable for 800k formatting?

Rick

 

[jongleur]

I haven't tried this myself,nut from what I've read it is best to use "new" media, at least unused media, and then only as an emergency disk.

I purchase new old stock every now and again to keep variety of unused media available, as well as keeping my old disks stored well.

As to where, well every now again someone here will post that they have spare old disks for sale, and there is always eBay, both for used media,as well as new old stock.

 

[gobabushka]

if you really have no other choice, put tape over the hole opposite the lock hole

 

[Ike]

putting tape over the hole works... most disks give you a formatting error... some do work though...

problem is... they only work for a few times. so dont expect any magic... you can use it for emergency transfers... but the best would be originals.

also, if you have a bulk eraser (or a degaussing coil for old CRT monitors or TV's), you can completely erase the magnetic tracks on already formatted 1.44 disks... rendering them as never used, making the chance of them working bigger.

 

[RickNel]

they only work for a few times.

Yes, there is even an Apple Support article that says that.

Does anybody know WHY that would happen? Do the re-formatted tracks somehow save a lower density signal? Normally, whatever is written to a magnetic medium (format or data) remains pretty stable. Even if some of the previous formatting (eg part of DOS 1.4mb tracks) is still present on the disk medium, why would it work a few times and then fail?

I'll be trying the bulk-erase method to see if I get better performance. I don't mind how many times I write the floppies, so long as I can get usable boot disks while I wait to get hold of some proper double-density disks.

Rick

 

[Dav]

In order of preference :

#1 : "New" DD disk

#2 : "Old" DD disk

#3 : "New" unformated HD disk with rubber on the right-hand notch

#4 : "New" formated HD disk with rubber on the right-hand notch

#5 : "Old" formated HD disk with rubber on the right-hand notch

... but perhaps used 90's HD disk quality is better than "newer" 2010's HD disk

Technicaly, HD disk with rubber on the right-hand notch goes well for me for making 400k and 800k disks for Plus and SE. I made them on a PowerMac 5180 (with Diskcopy only).

You can read on the internet that it's less reliable than real DD Disk. Perhaps.

In my opinion, as long as you keep the disk images on a safe place (CD + Cloud + PC), it's not a big deal. You can give a try on that solution. Write your disk labels with a word processor, print them on sticker paper, and save your disks labels with the disks images. I would be easyer and faster to remake your disks if something goes wrong with time.

I think you should prefer the superdrive if you have a lot of disks to copy, just to save your 800k drive (it's easyer to find working 1.4 mb superdrive than old 800k drive).

But from an historical / musealistic / aesthetical point of view ... HD disk with rubber is not very nice.

If you can, the best solution is to buy an old stock from "new" DD disk (i bought for myself a stock of very nice cream-white generic blank DD disk at cheap price). I think your 512ke deserve it.

 

[RickNel]

When I think about it, a drive that can write 1.4mb is probably writing more tracks per side than a drive that writes 720-800k.

I know that is the case with using a DVD writer to make a CD - it simply writes fewer tracks and leaves bigger gaps between tracks, which is why some older CD players calibrated for wider tracks have trouble with DVD-written CDs.

If so, then a Superdrive would be writing narrower tracks which would hold a lower detectable charge. A disk written to 800k format by a Superdrive might be leaving traces of any previous format in between the new tracks. Such a disk could be read well by a Superdrive, but less well by a 800k original drive.

This still does not explain why such disks can be read a few times, then fail, consistently.

Rick

 

[krye]

The track spacing is different between 1.44s an 800s. It's like formatting a DVD as a CD-R. (Not that you can actually do that, but the analogy stands.) Data integrity falls through the floor when you do this. It'll work in a pinch for a simple file transfer, but not as a means for any kind of long-term storage. The disk will fail.

Definitely in the case if the 1.44M floppy was formatted as such before hand. So if the box says "Formatted for IBM-PC" or "Formatted for Macintosh", they're be problematic. When you format it as 800K, the track spacing changes, but those old 1.44 tracks are still interleaved in between. They're reel havoc on your data integrity. You'll have serious read/write errors. The only way you can improve that is to use 1.44s that have never been formatted before. But even still, it comes back to the whole "it'll work in a pinch, but not for the long term". A floppy is not just a floppy.

 

[Gorgonops]

When I think about it, a drive that can write 1.4mb is probably writing more tracks per side than a drive that writes 720-800k

The track spacing is different between 1.44s an 800s.

NO.

If you're an old-enough timer you *may* confusing the issues with high vs. low density media with the additional track-spacing difference between 1.2Mb and 360k PC floppies. In that case, in addition to writing more bits-per-track the higher-density drive used 96 tracks per inch verses the 48TPI of the lower capacity. Because the tighter track spacing the higher density drive has a narrower read/write head, and that creates issues like what kyre described when trying to use the *higher density drive* to write to lower density disks which will be later read in an actual low-density drive, IE, the higher density drive would only overwrite *half* of what the low density drive put on the disk. Insert the disk into a real low density drive and the wider head will be able to see both the old and new data. This problem basically necessitated having to bulk-erase and format *on the high density drive using the low density mode* any media you wanted to use to carry data from the newer machine to the old one.

Both 800k (720k, DD) and 1.44MB (HD) 3.5 inch mechanisms use an identical 135 TPI track density and spacing so there's no "interleaving problem". The problem with using the higher density disks in the lower density drive are exclusively due to the differing magnetic properties of the media, IE, the higher density recording uses a higher write current on a less-easily-magnetized media in order to minimize crosstalk between bits that are more tightly packed than those recorded by the lower density devices. What this means in practice is:

A: Using a high-density disk in a low density drive will never be completely reliable even under the best of circumstances. Yes, there are plenty of people on the internet that will tell you they've gotten away with doing it for years and it seems to work fine, but the fact is that the strength of the magnetic field generated by the read-write head in a DD drive will make a weaker "imprint" on the disk than it should. This is why even a disk that formats okay may randomly fail soon afterward; you're essentially writing your data in disappearing ink.

B: If you do insist on it you pretty much either have to bulk-erase your HD disks or format them multiple times. The 800k drive will already be having trouble making its mark on the media, it's going to have a doubly-hard time overwriting the magnetic footprints left by the higher-strength magnetic field that was at work if the disk was *ever* formatted to its full 1.44mb capacity. (In the later years of floppy disk production almost all floppies came with a DOS format on them from the factory, that counts.) Again, *THIS* is why the disk ever being formatted matters, not a "track interleave" problem.

Note, of course, that 1.44MB drives automatically switch to the lower write current used by 720/800k drives when writing at the lower density. So sticking a piece of tape over the density detection window and formatting your HD disk in a 1.44mb drive isn't going to do any better job making a "compatible" disk than formatting it in the real McCoy.

floppydisk.com has 720k disks for a buck each. Yes, that's semi-pricey. But if you don't need a million of them it's an option.

 

[krye]

...and the wider head will be able to see both the old and new data....

That's what I meant by interleaving. You'd have something like this: (forgive the crude image, but I'm on a PC at work and the tools are limited.)

I'm trying to illustrate that the old data and new data are both visible on the same track. Ergo: read/write errors.



PS - you can get DSDDs on eBay for way less than a buck a piece. <2cents>They're cheap enough that it's worth it to just buy a 10-pk and not muck around with the 1.44s and risk data loss.2cents>

 

[Gorgonops]

That's what I meant by interleaving. You'd have something like this

Yes, that totally illustrates the problem with 1.2MB 5 1/4" floppies. It just doesn't apply to 3.5".

For the 3.5" version you could show a track of bits written by the HD format as a stream of dots which are completely solid red, while the weaker format from the DD drive/format gets layered on top as a roughly 70% opaque green. The red will still show through, just in a different way.

 

[RickNel]

Thanks guys - this is the information I was looking for. Does this summarize it ?

The magnetic coating on a 3.5" HD floppy is calibrated to record with a higher charging current than the coating on DD floppies.

A drive that detects a DD disk will only write at the lower current standard for DD disk magnetic coating.

As a result,

a) the new written DD signal will be weaker than specified for HD medium

B) any data or format information previously written at HD current level will not be fully erased by a DD write operation

c) the ghost of previous HD data or format may last longer than the DD signals that are written over it.

Logically, if a more thoroughly magnetized HD "ghost" signal persists in the coating medium, it could over a period of time re-magnetize the weaker DD signal, the way any permanent magnet will do. In fact, this would happen even if the disk is bulk-erased or de-gaussed before a DD write, because whatever polarity is written as a particular DD signal point will eventually be affected by polarity of neighbouring molecules that did not take up the weaker DD charge.

I can see that this is a greater problem for diskettes than for CDs. CD/DVD signals are recorded as binary on/off optical bits, so there is quite a wide range of tolerance for stronger or weaker laser reads and writes. But floppies record a frequency modulated (FM) signal with a carrier frequency that is much higher than the data rate. This would be very prone to failure as the signal fades or degrades, as we know from floppies in long-term storage.

5.25" floppies retain data generally longer than 3.5" floppies - I have some that are 35 years old and still can be read.

I've ordered some DD disks.

Rick