English Amiga Board


Go Back   English Amiga Board > Main > Retrogaming General Discussion

 
 
Thread Tools
Old 13 May 2020, 17:40   #1
monty359
Registered User

monty359's Avatar
 
Join Date: Nov 2013
Location: cornwall uk
Posts: 27
single sided disks?

i was wondering something, as i dont have a clue.. (been out the loop too long so forgot everything)

if a disk says 'single sided' on it, can that be used on amiga?
(and even if there was a single sided disk, cant u just write to the other side anyway?)
monty359 is offline  
Old 13 May 2020, 18:09   #2
Juz400
Registered User

 
Join Date: Mar 2017
Location: London
Posts: 105
Simple answer YES
I used many Atari single sided disks on Amiga, they put the same coating on both sides of the media, they are only `labeled` single sided to give you that `reassurance`
Juz400 is offline  
Old 13 May 2020, 18:33   #3
Gorf
Registered User

 
Join Date: May 2017
Location: Munich/Bavaria
Posts: 1,144
There a re many floppy-disk variants and formats. Among them very strange ones.
But usually for 3.5 inch disk it means that is was written by or for a single-sided drive.

That means the disk had to be ejected, flipped over and inserted again to read the other side - but both sides contain data!

now can you read it with a double-sided drive?
usually not - or not the way one would expect!

since you are supposed to flip the disk, the data on the other side is written in the opposite direction. So to read it on a double-sides drive, you have to use it in the same manner an a single-sided drive and use only one read-head at the same time and flip the disk to access the other side..

since the Amiga had double-head-drives from the beginning, it can't be an amiga disk.
if you want to access the data on it, you would need to know for what system this disk was meant for ...

If you just want to format this disk and use it as normal: go ahead!

Last edited by Gorf; 13 May 2020 at 18:42.
Gorf is offline  
Old 14 May 2020, 02:09   #4
monty359
Registered User

monty359's Avatar
 
Join Date: Nov 2013
Location: cornwall uk
Posts: 27
cool, thanks guys

yes would just reformat them anyway so thats all ok
monty359 is offline  
Old 14 May 2020, 20:48   #5
dirk_the_daring
Registered User

dirk_the_daring's Avatar
 
Join Date: Oct 2008
Location: Alicante / Spain
Posts: 131
Quote:
Originally Posted by Gorf View Post
There a re many floppy-disk variants and formats. Among them very strange ones.
But usually for 3.5 inch disk it means that is was written by or for a single-sided drive.

That means the disk had to be ejected, flipped over and inserted again to read the other side - but both sides contain data!

now can you read it with a double-sided drive?
usually not - or not the way one would expect!

since you are supposed to flip the disk, the data on the other side is written in the opposite direction. So to read it on a double-sides drive, you have to use it in the same manner an a single-sided drive and use only one read-head at the same time and flip the disk to access the other side..

since the Amiga had double-head-drives from the beginning, it can't be an amiga disk.
if you want to access the data on it, you would need to know for what system this disk was meant for ...

If you just want to format this disk and use it as normal: go ahead!

But indeed single sided floppies work perfect on my old A500, back then with my Amiga the shop gave me a floppy box with 8DD and 2 single sided by mistake, I used them a lot, and they are still working. One has Menace copy and the other Speedball and both games worked perfectly from begining to end with no errors, I completed them several times.

Last edited by dirk_the_daring; 14 May 2020 at 20:55.
dirk_the_daring is offline  
Old 14 May 2020, 21:37   #6
BarryB
Amigaholic

 
Join Date: Dec 2009
Location: UK
Posts: 3,309
Quote:
Originally Posted by Gorf View Post
There a re many floppy-disk variants and formats. Among them very strange ones.
But usually for 3.5 inch disk it means that is was written by or for a single-sided drive.

That means the disk had to be ejected, flipped over and inserted again to read the other side - but both sides contain data!

now can you read it with a double-sided drive?
usually not - or not the way one would expect!

since you are supposed to flip the disk, the data on the other side is written in the opposite direction. So to read it on a double-sides drive, you have to use it in the same manner an a single-sided drive and use only one read-head at the same time and flip the disk to access the other side..

since the Amiga had double-head-drives from the beginning, it can't be an amiga disk.
if you want to access the data on it, you would need to know for what system this disk was meant for ...

If you just want to format this disk and use it as normal: go ahead!
Except you can't 'flip' a 3.5" disk, so if your drive was single sided you could only use one side of the disk not the other! Commodore 64 5.25" disks and Spectrum/Amstrad 3" disks could be 'flipped' though! In fact I believe all 5.25" and 3" disks could be 'flipped' to use the other side if needed!
BarryB is offline  
Old 14 May 2020, 23:23   #7
Gorf
Registered User

 
Join Date: May 2017
Location: Munich/Bavaria
Posts: 1,144
Quote:
Originally Posted by BarryB View Post
Except you can't 'flip' a 3.5" disk, so if your drive was single sided you could only use one side of the disk not the other! Commodore 64 5.25" disks and Spectrum/Amstrad 3" disks could be 'flipped' though! In fact I believe all 5.25" and 3" disks could be 'flipped' to use the other side if needed!
ok - I assumed single-sided 3.5'' drives would behave like the their 5.25'' and 3'' counterparts. Did not now that they really only could use one side ...
Thanks!

luckily the disks themself are coated on both sides nevertheless.
Gorf is offline  
Old 14 May 2020, 23:27   #8
Gorf
Registered User

 
Join Date: May 2017
Location: Munich/Bavaria
Posts: 1,144
Quote:
Originally Posted by dirk_the_daring View Post
But indeed single sided floppies work perfect on my old A500, back then with my Amiga the shop gave me a floppy box with 8DD and 2 single sided by mistake, I used them a lot, and they are still working. One has Menace copy and the other Speedball and both games worked perfectly from begining to end with no errors, I completed them several times.
that is want I meant by "using them as normal" - it works.
Gorf is offline  
Old 15 May 2020, 00:29   #9
BarryB
Amigaholic

 
Join Date: Dec 2009
Location: UK
Posts: 3,309
Quote:
Originally Posted by Gorf View Post
ok - I assumed single-sided 3.5'' drives would behave like the their 5.25'' and 3'' counterparts. Did not now that they really only could use one side ...
Thanks!

luckily the disks themself are coated on both sides nevertheless.
The metal dust shutter on a 3.5" floppy disk only slides one way to open, so if you flip it and put it in the drive then the mechanism that slides the shutter open will jam as it can't mechanically locate the correct part of the disk that allows the shutter to be slid open.

Also, a 3.5" drive needs two heads to read/write to both sides of the disk. All single sided drives have a lower head to read/write to the underside of the disk and a double sided drive has an upper head to read/write to the topside of the disk as well.
BarryB is offline  
Old 15 May 2020, 02:36   #10
Gorf
Registered User

 
Join Date: May 2017
Location: Munich/Bavaria
Posts: 1,144
Quote:
Originally Posted by BarryB View Post
The metal dust shutter on a 3.5" floppy disk only slides one way to open, so if you flip it and put it in the drive then the mechanism that slides the shutter open will jam as it can't mechanically locate the correct part of the disk that allows the shutter to be slid open.
yes, that would make the mechanics more complicated, but I guess the orientation could be (mechanically) detected by the flattened corner of the disk.
flat corner on the right, move slider to the left and vice versa...

Quote:
Also, a 3.5" drive needs two heads to read/write to both sides of the disk. All single sided drives have a lower head to read/write to the underside of the disk and a double sided drive has an upper head to read/write to the topside of the disk as well.
true - that's why on 5.25'' disk formatted for a mono-head-drive ("flip over")
is incompatible with a dual-headed drive, since the data on the other side are written in the opposite direction, because the drive spins always in the same direction
(this problem occurs on late dual-headed drives for the C64/C128)
... same would be true for a 3.5'' singe sided disk, if a mono-headed drive with flip-over would exist.
Gorf is offline  
Old 15 May 2020, 08:49   #11
Amigajay
Registered User
 
Join Date: Jan 2010
Location: >
Posts: 2,292
Quote:
Originally Posted by Gorf View Post
ok - I assumed single-sided 3.5'' drives would behave like the their 5.25'' and 3'' counterparts. Did not now that they really only could use one side ...
Thanks!

luckily the disks themself are coated on both sides nevertheless.
Yeah this was a big problem for early Atari ST developers as for a year or two ST models only came with single sided drives, when they upgraded them to double sided drives publishers still had to include two sets of disks as they didn’t know what drive each consumer had! Even Lemmings still had this in 1991, i don’t know how many other games had both sets included, seemed a right mess, one thing Commodore got right from the off!

Edit: further to the above, publishers as well as either deciding to include both sets of disks at extra cost, more often than not just included single sided disks.
I.e Indiana Jones Last Crusade - 3 disks Amiga, 6 disks Atari ST, just so early adopters weren’t alienated, but imagine twice the amount of disk swapping!

Last edited by Amigajay; 15 May 2020 at 14:18.
Amigajay is offline  
Old 15 May 2020, 13:09   #12
AMIGASYSTEM
Registered User
AMIGASYSTEM's Avatar
 
Join Date: Aug 2014
Location: Brindisi (Italy)
Posts: 5,802
I have never used Floppy 3.5 a single sided but I read on the attached screenshot that they have a capacity of only 320Kb

AMIGASYSTEM is offline  
Old 15 May 2020, 13:28   #13
Hewitson
Registered User
Hewitson's Avatar
 
Join Date: Feb 2007
Location: Melbourne, Australia
Age: 37
Posts: 3,737
Quote:
Originally Posted by AMIGASYSTEM View Post
I have never used Floppy 3.5 a single sided but I read on the attached screenshot that they have a capacity of only 320Kb

That would be after being formatted for a particular filesystem. The disk should be 500KB unformatted.
Hewitson is offline  
Old 15 May 2020, 13:39   #14
Gorf
Registered User

 
Join Date: May 2017
Location: Munich/Bavaria
Posts: 1,144
Quote:
Originally Posted by Hewitson View Post
That would be after being formatted for a particular filesystem. The disk should be 500KB unformatted.
Per side... since you can use it as a regular double sided disk in all cases we are aware of, is is 1Mb in total.
Gorf is offline  
Old 15 May 2020, 13:46   #15
Hewitson
Registered User
Hewitson's Avatar
 
Join Date: Feb 2007
Location: Melbourne, Australia
Age: 37
Posts: 3,737
Quote:
Originally Posted by Gorf View Post
Per side... since you can use it as a regular double sided disk in all cases we are aware of, is is 1Mb in total.
You can drill a hole in a DD disk and use it as a HD disk, too. That doesn't mean that it is recommended.
Hewitson is offline  
Old 15 May 2020, 13:55   #16
Gorf
Registered User

 
Join Date: May 2017
Location: Munich/Bavaria
Posts: 1,144
Quote:
Originally Posted by Hewitson View Post
You can drill a hole in a DD disk and use it as a HD disk, too. That doesn't mean that it is recommended.
In this case really different coatings are used - DD and HD disk are NOT the same.
But single sided DD disks are are, for all we know, exactly the same as double sided.

(And even if you could find a real single sided disk, with coating just on one side, it would simply not work at all as a double sided disk and you would notice immediately - other than with HD floppies.)
Gorf is offline  
Old 15 May 2020, 17:18   #17
AmigaHope
Registered User
 
Join Date: Sep 2006
Location: New Sandusky
Posts: 680
Almost every single-sided disk is really a double-sided disk sold as single sided. I have never, ever seen a truly single-sided 3.5" floppy.

The big distinction is that only one side of a single-sided floppy is guaranteed to work. For instance a manufacturer could have had a bad run of their floppy media where one side did not pass quality control. In cases like this they could sell these as single-sided, since a single sided drive would never even see the "bad" side of the disk.

Since manufacturers had to meet their orders for both single-sided and double-sided disks though, they would just produce a ton of double sided media, put any rejects into the single-sided disks, and then fill out the remainder of the order with perfectly good double-sided disks labeled as single-sided. If they're properly balancing for maximal economic output, they'd always make sure their media is as good as they can reasonably get it because the single-sided market was small, and make sure their "bad" media was always less than the single-sided demand -- as wasted runs are just lost money, especially if their QC is so bad that both sides turn out to be bad (thus rendering the product totally useless)

In most cases though a single-sided floppy should work fine as a double-sided. Just make sure you do a complete write+verify of both sides first, and understand that data on that disk may not be as reliable long-term even if it passes an initial test.

It's the same reason CPU and GPU manufacturers will sometimes sell 4-core CPUs as 2-core, or 52 compute unit GPUs as 36 compute unit. They have extra SKUS where they can sell chips where parts of them failed, but they match the market such that it always consumes all of their bad stock, and as their QA gets better they wind up selling CPUs with 4 good cores as 2-core and if an end-user is savvy enough they can unlock the other 2 cores for free.

Last edited by AmigaHope; 15 May 2020 at 17:25.
AmigaHope is offline  
Old 15 May 2020, 18:14   #18
Gorf
Registered User

 
Join Date: May 2017
Location: Munich/Bavaria
Posts: 1,144
well - manufacturers wouldn't test every single disk anyways, but take a certain amount of samples from each batch and test them - if these samples are ok, the whole batch would be declared fine.
This way you can ensure that the probability of a faulty disk is below a certain threshold, and minimize the time for testing.

and since the market for single sides disks was small in comparison, it made probably no sense to make a different product that would require a different production process.

so I somewhat doubt, they would pack up disks with a failure at just one side as single sided disks, but would more likely throw it away, since there was clearly something going wrong during the production.
but that is speculation of course.
Gorf is offline  
Old 15 May 2020, 18:42   #19
AMIGASYSTEM
Registered User
AMIGASYSTEM's Avatar
 
Join Date: Aug 2014
Location: Brindisi (Italy)
Posts: 5,802
Quote:
Originally Posted by Gorf View Post
In this case really different coatings are used - DD and HD disk are NOT the same..)
In fact, DD disks are thicker and store data more deeply while keeping data stored for longer.
AMIGASYSTEM is offline  
Old 15 May 2020, 20:15   #20
Gorf
Registered User

 
Join Date: May 2017
Location: Munich/Bavaria
Posts: 1,144
Quote:
Originally Posted by AMIGASYSTEM View Post
In fact, DD disks are thicker and store data more deeply while keeping data stored for longer.
that leads to the question if for an original Amiga-HD-drive (running at half speed) a modified DD disk is more suitable than a real HD-disk, since the write head generates still the same magnetic field and has (per bit) the same amount of time as in DD-mode
Gorf is offline  
 


Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools

Similar Threads
Thread Thread Starter Forum Replies Last Post
Single-sided PC/ST disk image support? mark_k support.WinUAE 16 23 August 2017 04:57
Single sided 8mb ram Gordon support.Hardware 3 18 April 2017 19:33
Wanted 32MB single sided 50-60ns 72 pin simm for Apollo 1240 chrisdew MarketPlace 4 15 December 2015 08:07
WANTED - 32MB Single Sided SIM for Apollo 1240 Card Peter MarketPlace 8 29 September 2010 17:44
Trade double sided128meg simm for single sided 64meg simm CU_AMiGA MarketPlace 0 13 November 2004 16:37

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT +2. The time now is 04:42.


Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2020, vBulletin Solutions Inc.
Page generated in 0.09347 seconds with 15 queries