Questions tagged [floppy-disk]

For questions related to the use, restoration and imaging of floppy disks.

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4
votes
1answer
95 views

What floppy disk format and layout and what disk image format are used for the Coleco Adam?

I just found out that emulators for the Coleco Adam use a disk image file format with the DSK file extension. This is a very very overused extension on many different disk formats. Though a few DSK ...
11
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4answers
2k views

Writting DSK images onto a 3'' floppy for Amstrad/Sinclair computers

For a project I'm working on, I need to write some disks to test on my Amstrad CPC 6128. I've got some 3'' inch blank disks, and all my Amstrad computers (CPC and PCW) have 3'' inch disks, as well as ...
6
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1answer
217 views

Did OSes write the floppy's logical sector number resulting from sector interleave/skew in the IDAM sector ID, or was it up to the OS?

I've been looking at MicroBee floppy disk image files. They use the DSK/EDSK image file format originally created for Amstrad CPC emulators, probably because both systems use derivatives of the CP/M 2....
3
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0answers
69 views

At which RAM address is the Microbee disk boot sector loaded and executed?

The Microbee was an early '80s Z80 microcomputer from Australia that was successful mostly in education. Looking at some disk image files I've downloaded I can see the disk layout seems to be very ...
13
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4answers
1k views

Can special tools recover data from floppy disks when Windows Explorer fails to do so?

I have many 1.44MB floppies 20 years old or older. My FDD, which I just bought online and received recently, cannot read them. The FDD can often display the contents of a floppy, but not successfully ...
4
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2answers
176 views

Why does Amiga 500 reset when reading a faulty disk

I have a copy of Syndicate disks for Amiga (I have original as well) and apparently the disk is damaged / faulty. It loads up to language selection menu, then tries to read disk and resets the ...
1
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0answers
43 views

What does a “DK” signature at the start of track 0 sector 3 of a Dragon 32/64 floppy disk?

I'm looking at disk image files for the Dragon 32 / Dragon 64 computers. The Dragon computers are very similar to the Tandy TRS-80 Color Computer "CoCo" but are not clones and are not the ...
1
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1answer
69 views

How many different standard boot sectors are there for Apple II DOS 3.3?

When formatting a blank 5¼ disk on an 8-bit Apple II using the INIT command, was there only ever one variation of the boot sector code that was written, or was it updated from time to time over the ...
4
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1answer
64 views

Determining which sectors in an Apple II floppy disk/image are used when the boot sector declares more than 1 sectors

The Apple II disk bootstrap process looks at the first byte of track zero sector zero to see how many sectors long the bootstrap code will be. It then loads these sectors at location 0x0800 and jumps ...
11
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4answers
952 views

Amiga floppy disks and GCR vs MFM

According to the Wikipedia article on GCR, the Commodore 1541 disk drive used a particularly efficient GCR encoding scheme to cram 170K onto the same 5.25" disks that in an Apple drive only ...
7
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1answer
107 views

Understanding the DMK disk image file format used by TRS-80 emulators

DMK is a low-level disk image file format used by TRS-80 Model I & Model III, Tandy Color Computer, Dragon 32 & 64, and MSX emulators. It's capable of representing copy-protected disks and all ...
3
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0answers
28 views

On the TRS-80 models I and III when is the directory track number written in the third byte of sector zero, and when in the second byte?

Earlier I had found that many but not all TRS-80 Model I and Model III disks begin with the three bytes 00h FEh 11h. This is the beginning of the boot sector where the CPU interpets it as a NOP ...
7
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2answers
1k views

Could Tandy TRS-80 Color Computers boot from disk at all?

I'm trying to find out if any of the Tandy CoCos could boot from disk. I'm thinking the answer is no but I'm having trouble confirming it. I believe that non-disk machines booted from the standard ...
4
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2answers
264 views

Can I still save data on a floppy that lost its magnetic charge over time

I have original Microsoft floppies, unfortunately they appear unreadable. Were stored in protector, in a box, in a dark and dry place for the last 20 years. No dust, moisture or exposure to magnetic ...
2
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1answer
47 views

What is the layout of the directory track on a TRS-80 Model I/Model III disk?

I've decided to add support for some more classic Z80 computers I used to use to my Ghidra modules, and the first Z80 systems I used were the TRS-80 model I and model III. I've found documentation ...
6
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1answer
447 views

Which DOS for a TRS-80 Model 4P?

Looking at the TRS-80 Disk Software Page, there's a rather extensive selection of DOS options that seem to work with the 4P and also claim high compatibility with the Tandy "TRSDOS" option. ...
4
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3answers
935 views

What are D64, T64, D71 and D81 files?

The docs for the Ultimate-II+ expansion cartridge for the Commodore 64 state: It is able to read D64 files, as well as D71 and D81 files (no partitions), T64 files. So what are D64, T64, D71 and ...
3
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1answer
77 views

Converting Apple II ProDOS blocks to DOS tracks and sectors

The 8-bit Apple II had two disk operating systems with different disk access semantics. DOS used tracks and sectors. A sector is 256 bytes. ProDOS used blocks. A block is 512 bytes. But mapping ...
0
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2answers
72 views

Reading 360k floppy disk in 1.2M drive

I formatted several 5.25" diskettes with 360k and 1.2M on the Windows XP PC using 1.2M (HD) drive. I am using the same drive to read data from 360k diskette back using custom driver. The controller ...
3
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2answers
91 views

Is there a “most correct” name for the disk format / filesystem used by Amstrads and Spectrum +3's?

The native floppy disk format/layout or "filesystem" used by Amstrad microcomputers such as the CPC and PCW range and by the Sinclair Spectrum +3 are versions of one that came from CP/M. In Amstrad ...
6
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2answers
564 views

How could a 16-sector PROM Apple II access a 13-sector disk?

When the Disk ][ first came out for the Apple II, the PROMs on the interface card only knew how to work with a 13-sector format. Around 1980, the Disk ][ was updated with 16-sector PROMs either for ...
29
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4answers
1k views

Absolute maximum number of nibbles on an Apple II floppy disk track?

The Apple 2's disk drive controller and 5¼" floppy disks have the following metrics: The disks is spun at (roughly) 300 RPM (Revolutions per Minute), which means it takes = 1000 ms/sec / (300 RPM / ...
10
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1answer
109 views

In TRS-80 parlance when talking about disks, what are “granules” and “lumps”?

In my reading to try to learn about the disk layout, directory, and boot process of TRS-80 Model I and Model III, I see some unusual words come up again and again. Along with the common terms "track" ...
3
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1answer
81 views

What is the process for TRS-80 Model I & III to boot from disk?

I can find enough mentions of bootable disks for TRS-80 Model I and Model III to be confident that they could boot from disk, but so far I'm failing to find much info on how that worked. In ...
3
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2answers
524 views

What file formats were used for binary executable files on later Sinclair ZX Spectrums?

The last official version of the Sinclair ZX Spectrum was the +3, released after the company was owned by Amstrad. It included a 3-inch floppy disk drive as used on other Amstrad computers. But even ...
3
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1answer
78 views

Where can this “boot.B” file be coming from on this Spectrum TR-DOS disk image?

After working on some tools that parse the TR-DOS disk image format .TRD files for a while I just noticed that one of the game disk images I had downloaded "La Abadia Del Crimen", only has three files ...
3
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1answer
572 views

Problem reading 720KB floppy disks containing dat [closed]

I am using a USB connected "Sabrent FD-05PUB" 3.5" floppy drive to read data using Windows 10 computer. It shows in Device Manager as "TEAC USB UF000x USB Device" The 1.44MB disks read just fine. All ...
4
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2answers
140 views

How did the Spectrum clones with TR-DOS and paged memory load and run code files from disk?

I've been playing with Spectrum emulators, their file formats and some reverse engineering tools recently. Thanks to this forum, I was able to parse the TR-DOS disk image format and find the bytes of ...
8
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8answers
3k views

Were any external disk drives stacked vertically?

There was a time when floppy disk drives were big, expensive devices that in many cases, instead of being components of a computer, would be separate machines connected by a cable, in some cases with ...
1
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1answer
135 views

How does the Spectrum +3 know how many files are in the disk's directory?

The Spectrum+3 uses a version of the Amstrad and CP/M disk layout. The Speccy version has a directory at the start of the disk after any reserved tracks and it can hold up to 64 files. Each ...
13
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5answers
1k views

How are blocks stacked on a floppy or older HD

I tried to understand how to read a floppy image format (.sdk). The format is based on CP/M 2.2 filesystem. I've lost track, and I think it's my third attempt. Now I am looking more into what these ...
16
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9answers
9k views

Formatting a 720K floppy disk over USB fails with Windows 10

I've read many times that USB floppy drives will not format (or read/write) 720K disks. But then I read several posts online where people say they have done it. Even with Windows 10 (which is what I'...
0
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2answers
132 views

Can I use a 2.88MB ed floppy disk (3.5in) in a drive that uses the standard 1.44 HD DS disk?

I am using a Windows XP with an old accounting app, that will only back up to a 3.5 in floppy disk. But the backup requires a second disk to complete the job -- a pain. Would a ed 2.88 mb floppy (if ...
0
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1answer
132 views

What did “double track” meaning in relation to floppy disks?

I mostly used 3½″ floppies back in the day but I also used 5¼″ floppies to some extent on Apple II's and TRS-80's. I was never exposed to 3″ floppy disks as used mainly on Amstrad microcomputers and ...
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0answers
48 views

Transfer a TeleDisk image of a 5.25 disk to a 3.5 disk

I am trying to power on an old Siemens PG675. It need a 5.25 disk but unfortunately it is missing. I found a TeleDisk image (.TD0) of this disk, and I would like to transfer it to a 3.5 floppy disk (I ...
4
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4answers
955 views

How does the Spectrum +3 know whether a disk is bootable or not?

I've been looking through documentation on The Sinclair/Amstrad Spectrum +3 which was the only Spectrum that came with a built-in floppy disk drive. The disk format was based on The Amstrad CPC and ...
3
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2answers
157 views

Why did the Apple Disk II version 3.3 change the boot protocol?

From what I understand, early versions of the Disk Controller II required that there never be two or more consecutive bit times without a phase transition (which would read as "0") but an upgrade to ...
8
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2answers
1k views

Transferring data from Spectrum +3 disk to tape/.TAP etc

I've recently found a number of my own programs (very old!) on Spectrum +3 discs, and I'm about to get hold of a working +3. Assuming the discs are readable, I'd like to transfer the programs (mostly ...
8
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2answers
352 views

What are the most common Apple II disk image formats and what hardware disk drive emulators can use them?

Archive.org has plenty of Apple II disk images, such as this DOS 3.3 image which is a .dsk file. I also see .nib and .d13 files, e.g. in this ASIMOV LISP collection. There seem to be further formats ...
13
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0answers
451 views

Oxford C compiler for Commodore 64

I kept one floppy from my Commodore 128 (which I used mostly in C64 mode), which is written Oxford C compiler. It is a 5.25" floppy. Don't ask me why I kept just this one; probably because I thought I ...
5
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2answers
813 views

Can a Harlequin ZX Spectrum clone be modifed to run CP/M?

The ZX Spectrum (and therefore the Harlequin) has its ROM from $0000 to $3FFF, while RAM further up to $5AFF is used for the screen (see Memory-Map). As CP/M expects RAM from $0000 upwards the two are ...
0
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2answers
120 views

How do I know where the file directory is stored on a Spectrum +3 disk layout?

I'm trying to parse Spectrum +3 disk images. I only ever had a tape-based Speccy back in the day. The +3 had a built-in floppy drive but was late to the party and not that successful. It had the same ...
6
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2answers
392 views

What's the timeline of Commodore diskette drives?

Commodore produced a number of different floppy diskette drive units, both 8" and 5.25", over the course of its history. Can someone provide a chronological list of the drives, their release dates, ...
2
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0answers
119 views

Algorithm to properly format 360k 5.25" diskette on 1.2M drive?

This is a low level tech question, as I develop the driver for the FDC at its command set level. Having reviewed a number of sources I can not find the algorithm of how to format the 360k diskette ...
6
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2answers
194 views

Why does _Beneath Apple DOS_ show FM encoding rather than GCR?

From the beginning in 1978 the Apple II floppy disk system used GCR encoding to convert data bytes to sequences of binary values to be written to the diskette: first 4-and-4 encoding (never released), ...
10
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3answers
913 views

Transferring files between Commodore PET and IBM PC

Suppose you have two early eighties computers, a Commodore PET with 8050 disk drive and an IBM PC with its 5.25" disk drive. Is there a way to transfer files between them? Not machine code programs, ...
11
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2answers
2k views

Weak bits on floppy for copy protection

How did the vendors using copy protection create weak bits on the floppies? This always fascinated me as a kid. I ended up finding a weak bit emulator that would intercept the floppy disk interrupt ...
5
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2answers
159 views

Mismatched floppy disk/drive reading and writing, what should one keep in mind?

Mismatched disk/drive refers to, for example, reading/writing a 720K disk with a 1.44M drive. Don't forget LS-120 and LS-240 SuperDisk drives, they can use standard floppies too. What can and can't ...
10
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2answers
882 views

What physical size and density floppies are the intermediate-capacity options for the /F switch of the DOS/Windows/OS/2 FORMAT command meant for?

In MS-DOS 5.0 and newer, PC-DOS 5.0 and newer, Windows 9x, Windows NT 3.1-2000, and OS/2 4.x, the FORMAT command (present in some form or another in literally every single version of Q/86-/MS-/PC-DOS, ...
19
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1answer
2k views

When low-level formatting a floppy, how does one ensure any existing sector markers are overwritten?

If a formatted floppy diskette is reformatted with a low-level¹ format, how does the formatting routine make sure that any previous sector markers are fully overwritten? In particular, how does it ...