Amiga.org
Amiga computer related discussion => Amiga Software Issues and Discussion => Topic started by: Blinx123 on December 15, 2012, 09:58:45 PM
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The severe lack of Amiga tech (which also includes original blank Amiga floppies) in my area had me thinking.
Are those 720kb IBM double-density floppies physically any different from 880kb Amiga double density floppies? Or is this simply a matter of formating these? e. g. could I take a 720kb IBM floppy, format it in CrossDos and write data from an 880kb ADF to it?
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No, they are no different. Just make sure you are using true 720K (DD) disks and not High Density disks.
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No, they are no different. Just make sure you are using true 720K (DD) disks and not High Density disks.
Nice. Thank you very much.
What would be the actual size of a 720kb/880kb floppy then? 960kb?
Seems kind of unreasonable of IBM to waste such a large amount of memory. Is there any particular reason why they did it (copy protection/performance/etc)?
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DD floppies are 1MB, HD 2MB (in raw capacity, theoretically so to say). Different computers have different efficiency when formatting.
PCs format them at 720KB. Amiga at 880KB.
I'm not quite sure what are you trying to do ?
If you insert a DD floppy in your Amiga, and format it, it will have 880KB free space. And you can write ADFs on it.
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DD floppies are 1MB, HD 2MB. Different computers have different efficiency when formatting.
PCs format them at 720KB. Amiga at 880KB.
I'm not quite sure what are you trying to do ?
If you insert a DD floppy in your Amiga, and format it, it will have 880KB free space. And you can write ADFs on it.
I have a whole bunch of big-box IBM/Tandy games that I'd like to convert to their respective Amiga releases.
Since x86 distanced itself so much from it's own past, I'm not feeling the vibe while playing these games on my PC*
*An Intel i5 2500k rig with a 2GB GTX 680, 16GB RAM a 1TB hardisc and a Blu-Ray drive running those games in Dosbox and outputting them to a 47" TV might sound awesome, but there's nothing classic about it.
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The unformatted capacity is actually 1MB.
The reason it's only 720KB is because the floppy controller in an IBM PC is actually an NEC PD765A - or at least compatible. Even on the southbridge chips of modern PCs, it's basically an adaptation of that same chip which was used so much in the early 80's (Spectrums, Amstrads etc.).
The PD765A isn't a very advanced chip - it requires certain sync signals and certain gaps between the sectors. Paula, on the other hand, is much more versatile, so the Amiga has the same MFM system, but with more efficient usage of the space on the disk. The WD1770 like in the BBC B and Atari ST is slightly better than the PD765, but not much, and is pretty much compatible, which is why STs can read PC disks easily, but not the other way round (and why the ST usually only has 360KB/720KB disks too).
So the reason that there's so much space wasted is simply because IBM used a generic controller chip in the original IBM PC, and it never changed (even to this day), whereas more advanced machines like the Amiga had much lower level access, and could do clever things like change the length of the dead space between sectors, which were unchangeable on the 765.
Incidentally, Microsoft did use a different system (Distribution Media Format - DMF) to get more information on floppy disks. They did this by changing the filesystem (limiting the amount of files available), and also by changing the sectors per track. I can only imagine that the 765A is capable of *reading* with a shorter inter-sector gap than it is _writing_ (which would make sense as it's just waiting for a sync signal - it would only be writing where it would be fixed how much data it was writing).
I intend to add support for DMF at some point in the Catweasel drivers....
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Since x86 distanced itself so much from it's own past, I'm not feeling the vibe while playing these games on my PC*
*An Intel i5 2500k rig with a 2GB GTX 680, 16GB RAM a 1TB hardisc and a Blu-Ray drive running those games in Dosbox and outputting them to a 47" TV might sound awesome, but there's nothing classic about it.
That's why you grab a cheap 386/486 and throw MS-DOS 6 on there ;)
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So the reason that there's so much space wasted is simply because IBM used a generic controller chip in the original IBM PC, and it never changed (even to this day), whereas more advanced machines like the Amiga had much lower level access, and could do clever things like change the length of the dead space between sectors, which were unchangeable on the 765.
The Amiga doesn't need any space between sectors because it can only read or write a whole track at a time. The controller chip in the PC is actually far more advanced than the rather brain dead controller in the Amiga.
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That's why you grab a cheap 386/486 and throw MS-DOS 6 on there ;)
True.
But that's kinda silly.
A) MS-DOS, while certainly better than Windows Vista, is still nowhere near as good as Amiga OS 3.1
B) An Amiga is such a classic because it never had a true successor. A 386/486 is just another PC and therefore really pales in comparison.
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So the reason that there's so much space wasted is simply because IBM used a generic controller chip in the original IBM PC, and it never changed (even to this day), whereas more advanced machines like the Amiga had much lower level access, and could do clever things like change the length of the dead space between sectors, which were unchangeable on the 765.
Basically PC's can write individual sectors, which means they need a sync marker and a gap between each sector. Because of drive speed tolerances they were quite pessimistic when choosing the gap size. When writing it has to read until it finds the correct sector header and then switch to writing.
The Amiga can only write full tracks, because there is only one sync and one gap per track. It can't do sector writing because it has no controller. When writing PC format disks it has to write a full track at a time.
So the Amiga has more space, but it's slower to read and write.
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You are, of course, correct. It's been a while since I looked at Amiga encoded disks. :)
I guess using the 765a makes the software a lot simpler (it just requests data at a particular location) but means it's much more limited because of it.
The Amiga I believe is basically just Paula chucking out bits which then have to get decoded, isn't it? I.e. great for copy protection, not so great for ease of use (hence Kickstart routines).
The usual way for copy protection on the 8-bits - and I'd guess the PC too - was to have illegal sector numbers in the sector headers. So the first track may have sectors 1,2,3,33,4,5,6,7,8,9 or something, which of course the DOS would think was an error.
Equally, nasty copy protections could do things like have sectors 1,2,3,1,2,3,4 on the disk which could never be written normally, but you could read all the sectors and check the existence of two different sector 1s, two sector 2s, that sort of thing.
Is this OT now? Sorry. :)
Edit: If you need to run old PC games, get a bridgeboard! You need a big box Amiga though (unless you're happy with CGA 8088/286 games :) )
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Use on PC side to format floppy:
"FORMAT A: /T:80 /N:9"
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I have a whole bunch of big-box IBM/Tandy games that I'd like to convert to their respective Amiga releases.
That's a good plan :)
Just go for it. There are no PC and Amiga disks. Just DD floppies. Put them in your Amiga and format them at 880K. A good recipe to enjoy the holidays :)
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Don't use the original PC disks though! Use blank disks. That way you can run both and see just how much better the Miggy was in the 80's/early 90's.
If you want cheap blank disks just get them used on eBay. You can still use most of them. Heck, if you're in the UK, I have tons you can have some of for postage.
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I guess using the 765a makes the software a lot simpler (it just requests data at a particular location) but means it's much more limited because of it.
The Amiga I believe is basically just Paula chucking out bits which then have to get decoded, isn't it? I.e. great for copy protection, not so great for ease of use (hence Kickstart routines).
The PC was built from off the shelf parts and the upd765a was basically all that was available, you can make an argument for sector gaps or a track gap but what was available to them had sector gaps so it wasn't really a choice.
The Amiga had a better price/performance ratio because everything as custom and having a track gap is easier from the hardware point of view, so it was cheaper for them to design and build. The greater storage space was a side effect of that, I doubt they ever considered doing it any other way.
trackdisk.device would have existed no matter how the hardware worked though. Even on the PC you wouldn't talk directly to the floppy controller. The only real difference is that the Amiga generally uses the same code for booting from a floppy and once the operating system is loaded. While on the PC you have separate device drivers. Both ways have their merits.
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That's a good plan :)
Just go for it. There are no PC and Amiga disks. Just DD floppies. Put them in your Amiga and format them at 880K. A good recipe to enjoy the holidays :)
Will do.
I've also just acquired a PC copy of Walt Disney's Animation Studio (brand new and still in it's shrinkwrap. My collector's itch was strong that day. Very strong), which I'll gladly convert to Amiga.
That way, I can probably use the remaining last floppy (the Amiga version only requires three while the IBM/Tandy comes on a total of four) for saving animations.
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Can Windows 7 or 8 even recognise a floppy, they've disappeared from hardware are they still in the OS?
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Yes, I use floppies under W7.
Had to format them on Amiga though.
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Will do.
I've also just acquired a PC copy of Walt Disney's Animation Studio (brand new and still in it's shrinkwrap. My collector's itch was strong that day. Very strong), which I'll gladly convert to Amiga.
That way, I can probably use the remaining last floppy (the Amiga version only requires three while the IBM/Tandy comes on a total of four) for saving animations.
What, you bought a collectable software package, and now you're going to overwrite the disks? I'll just say I find that thinking very strange.
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What, you bought a collectable software package, and now you're going to overwrite the disks? I'll just say I find that thinking very strange.
Agreed. Just slap the Amiga version on some blank disks and throw them in the same box. First thing we did back in the day was to make backups of everything and keep them in the same place. It'll be just like that.
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Don't forget to add the Breadbox Ensemble GUI on top of the DOS:
http://www.breadbox.com/ensemble/geocats.asp?category=Ease-of-Use
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I tried turning on my Amiga 1200 for the first time today and already ran into some weird issue.
The workbench floppies I received with my Amiga 1200, although unused, are unreadable.
Whenever I try to boot from any of them, I'll be greeted with the very same message over and over "Not a valid DOS disk in drive DF0:".
Is this usually a hardware issue or something that can be solved by formating the floppies?
How do I find out if it's not my drive, besides throwing another bunch of floppies at it and potentially risking the life of perfectly fine floppies?
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Don't try to reformat your Workbench floppies unless you want to erase them entirely (that's part of what formatting does).
It very well could be they are just old floppies suffering from bit-rot. I.e. the magnetic data on them degrades over time. After 20 years, many good floppies are now unreadable.
You definitely should try formatting a spare floppy in that drive, though, to see if it works. You can't damage a floppy by trying to format it in a faulty drive (unless the drive head somehow crashes into the plastic surface of the media). At worst, you won't be able to format the disc, or you'll have a disc that is only readable with that particular drive (if the heads have gone out of alignment).
If your drive is out of alignment, then it will format discs only it will be able to read. But you can always re-format them when you get a repaired/new drive. Formatting is not permanent.
But how are you going to get into the OS in order to format the disks if you can't even boot Workbench?
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Frankly, I think it's the drive.
David (davideo) told me I should check again, perhaps remove and push in the disk a few times more and that's basically when the following happened.
1. The disk gets read a little while longer than before (like 8 seconds rather than 3 or less).
2. A message box pops up, saying there is an error on sector block 002.
3. (after I removed the disk and pushed 'retry' again) the drive starts acting up and begins to sound like a rattle snake.
4. (after I turned it off and back on) everything is back to normal and I get the "Not a valid DOS disk" error again.
I hope I didn't screw up a perfectly fine disk now.
I plan on asking my former boss for an HD floppy drive I could modify later today. It sucks, but I'll basically have to cut open the seal on my Amiga and see if there's something wrong inside and if I can't find anything, I'll have hook up that modified HD drive.
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Before you go hacking apart your A1200, wouldn't it be prudent to get a good known working disk and check if it has problems in your A1200?
That would be a lot less work and eliminate the chance of accidentally damaging your A1200.
You never said where you got those Workbench disks that are failing. Where did you get this A1200? Is it one of Petro's? Were the Workbench disks known to be working before you tried them?
As I said, 15 year old Workbench disks, even if never used, are not likely to be working after all this time.
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Before you go hacking apart your A1200, wouldn't it be prudent to get a good known working disk and check if it has problems in your A1200?
That would be a lot less work and eliminate the chance of accidentally damaging your A1200.
Sure. But isn't it rather telling already that those disks would all be accessed for less than 5 seconds? Even if the floppies were faulty, shouldn't it still take the drive a lot longer?
You never said where you got those Workbench disks that are failing. Where did you get this A1200? Is it one of Petro's? Where the Workbench disks known to be working before you tried them?
Yea. It's one of Petros and the disks were included. Everything was still sealed when I received it.
As I said, 15 year old Workbench disks, even if never used, are not likely to be working after all this time.
That's kinda sad.
I thought floppies were a bit more durable.
I guess that means most of my games will not work either anymore.
What a shame.
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I don't think 5 seconds is unusual for it to fail, especially if the boot block is damaged.
No, floppies are not durable media. Magnetic media is not the greatest for long term storage of digital data. Especially floppies.
Maybe some types of streaming tape drives are good for long term archival storage (like DDS tapes), but not 3.5" floppies.
It *could* be your drive has failed, but I would try the weakest link first - and that would be the floppy disks themselves.
Didn't the Magic Pack you received come with *any* other bootable disks you could try?
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I don't think 5 seconds is unusual for it to fail, especially if the boot block is damaged.
No, floppies are not durable media. Magnetic media is not the greatest for long term storage of digital data. Especially floppies.
Maybe some types of streaming tape drives are good for long term archival storage (like DDS tapes), but not 3.5" floppies.
It *could* be your drive has failed, but I would try the weakest link first - and that would be the floppy disks themselves.
Didn't the Magic Pack you received come with *any* other bootable disks you could try?
Yes. There were some other disks in there as well, but I really don't want to risk screwing them up, in case it's the drive that's failing.
Is there no other way to check whether the floppies are broken or not? Weren't there two or three Windows tools that made it possible to read Amiga floppy disks without the need of a catweasel?
Furthermore, if the workbench disks turn out to be the culprit, is there any way to install Amiga OS 3.1 without the need of a floppy drive? I don't want to spend money on another set of WB disks. Especially if there's a fair chance these might turn out to be faulty as well.
EDIT: Found the tool I was thinking about. It's called adfread. I'll still need an Amiga floppy drive for it, of course.
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I made a little YouTube video a little while back called "how to clean floppy disks". Might be worth a try.
Many apparently bad disks actually are just dirty and work fine when you've removed the dirt. Be aware though that if they do start working, make a backup immediately! It may have been oxidisation that broke the disk so you may have lost some of the surface.
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Yes. There were some other disks in there as well, but I really don't want to risk screwing them up, in case it's the drive that's failing.
A failing drive is not very likely to screw up a floppy disk unless it does some sort of write command to the disk (which is not the case when an Amiga boots). The only reason it would "screw up" a disk is if the drive head was rubbing against the disk surface - which is not likely to happen. I would just try it - seriously you don't have much to lose and even if a disk was damaged you can easily find the .adf for that bundled software and re-write them to new disks when you get the system working eventually.
Is there no other way to check whether the floppies are broken or not? Weren't there two or three Windows tools that made it possible to read Amiga floppy disks without the need of a catweasel? EDIT: Found the tool I was thinking about. It's called adfread. I'll still need an Amiga floppy drive for it, of course.
I think you are confused. This tool requires two regular PC floppy drives, not Amiga drives. You must have two floppy drives installed in your PC.
You must also have a PC motherboard that supports two floppy drives in the BIOS - many newer motherboards do not support this "legacy" feature. Do you have an old 486, Pentium I or II hanging around to do this with?
Other than that the ONLY way to read an Amiga disk in a PC is with a CatWeasel or another hardware device like a Kryoflux that reads foreign disk formats on the PC.
The only other ways to boot into Workbench are with a hard drive or CD/DVD drive. There are PCMIA and SD card solutions for the A1200, but I'm not sure if you can boot from them. Another option would be to get a Subway or other USB interface for the A1200, but again I'm not sure if it's bootable.
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PCs haven't come with any floppies for a few years now, but couldn't you just plug in a pair of usb floppy drives? The sell for for 5 or 10 bucks on eBay...
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PCs haven't come with any floppies for a few years now, but couldn't you just plug in a pair of usb floppy drives? The sell for for 5 or 10 bucks on eBay...
Good idea.
Gonna pay my former boss another visit after Christmas. I'm sure he can work something out. He's got plenty of floppy drives and quite a few ATA to USB adaptors.
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Not if he wants to use Amiga formatted floppies, no.
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You guys are confusing me.
Anyways. I've just plopped in another stack of floppies and neither worked. The disk would be read for 3 seconds upon which the aforementioned message would pop up.
Another thing I've just realized: whenever I remove a disk, the heads will make a short screeching sound and seem to slightly lower themselves.
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You guys are confusing me.
Anyways. I've just plopped in another stack of floppies and neither worked. The disk would be read for 3 seconds upon which the aforementioned message would pop up.
Another thing I've just realized: whenever I remove a disk, the heads will make a short screeching sound and seem to slightly lower themselves.
Sounds like the head guides and stepper-motor worm-drive just need re-greasing - hardly surprising for a 15 year old drive that's never been used.
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Sounds like the head guides and stepper-motor worm-drive just need re-greasing - hardly surprising for a 15 year old drive that's never been used.
Sounds plausible.
Thanks.
Are there any publicly available instructions I could download? I'm not very hardware savy (at least when it comes to non-synthetic/non-theoretic stuff).
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Sounds plausible.
Thanks.
Are there any publicly available instructions I could download? I'm not very hardware savy (at least when it comes to non-synthetic/non-theoretic stuff).
Yep:
- drive to electronics store, buy non-conductive electronics grade grease and isopropyl alcohol
- open case, remove fdd, remove fdd cover (if it has one), use isopropyl alcohol on lint free cloth to clean the long worm-drive gear etc and the 2 guides that the head mechanism slides up and down on (look for evidence of dry or old grease to know where to clean).
- apply grease to dry part of lint free cloth and thouroly cover areas just cleaned with fine coating of grease.
- plug drive back in with cover still off and use a head-cleaning disk on drive about a dozen times till you can see head mechanism moving smoothly and quietly.
that should do it and the heads will get a good clean too. :)
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Good idea.
Gonna pay my former boss another visit after Christmas. I'm sure he can work something out. He's got plenty of floppy drives and quite a few ATA to USB adaptors.
You could try this, but I suspect it won't work.
USB floppies (I suspect) are treated like Mass USB storage devices. I *suspect* that the USB drive gets mounted on the OS (Windows, etc.) as if it were just a generic USB storage device, and inside the drive there is some sort of hardware translator so that the drive's contents can be read and present to the OS (i.e. windows) is if it came off a USB mass storage device (i.e. a flash drive).
Because of this I'm guessing the software that runs accomplishes this dual-floppy hardware trick won't work with USB floppy drives.
When computers had internal floppy drives, the BIOS "knew" how to directly control the floppy drive. I suspect the floppy trick to read Amiga disks on a PC equipped with two PC drives needs these sort of internal BIOS instructions and the on-the-motherboard board floppy controller circuitry.
I'm guessing you will need a real PC that supports floppy drives in the BIOS and has a floppy connector on-board for this trick.
Still, might be worth a try. Let us know if it works.
Anyways. I've just plopped in another stack of floppies and neither worked. The disk would be read for 3 seconds upon which the aforementioned message would pop up.
When you say you plopped in another stack of floppies - you DO mean a set of Amiga formatted floppies, right? A set of new, blank, unformatted floppies or PC formatted floppies of course won't be recognized. Sorry to be pedantic, but I just want to be clear on that issue.
As for re-greasing the rails and worm screw of the floppy. That's a good idea and would certainly be one of the first things I would try.
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Just to be clear: A USB device will not work at all. The controller is completely wrong for Amiga formatted disks.
You need a specialised floppy controller like a Catweasel or Kryoflux, or you might get lucky with a PC's controller using the ADFread hack.
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When you say you plopped in another stack of floppies - you DO mean a set of Amiga formatted floppies, right? A set of new, blank, unformatted floppies or PC formatted floppies of course won't be recognized. Sorry to be pedantic, but I just want to be clear on that issue.
As for re-greasing the rails and worm screw of the floppy. That's a good idea and would certainly be one of the first things I would try.
Yes. A set of Amiga formatted floppies.
I tried Personal Paint, Wordworth, Whizz and Photogenics.
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Good idea.
Gonna pay my former boss another visit after Christmas. I'm sure he can work something out. He's got plenty of floppy drives and quite a few ATA to USB adaptors.
Oh, another thing. I don't think PC floppy drives use the ATA standard or ATA connectors. That was for IDE hard drives and stuff like that. PC (and Amiga) floppy drives used their own special ribbon connectors with 34 pins. So ATA to USB connectors won't work with PC floppy drives.
Oh, and when you open up your Amiga floppy drive and re-grease the rails and worm screw, please make sure you don't get any grease on the read/write heads.
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Or you could just by a head cleaning kit and clean the head. I had the same problem with a number of Amigas. Seems that some disks have this affect on the drive. never happens with any of my original disks, only with older copied disks that I acquire. I just drop the fluid on the cleaning disk and pop in the drive and all works fine.