These are used to essay implement completely transparent support for ibm pc format floppy disks, including the slightly different Atari st format. Computer Concepts released a package that implements an image filing system to allow access to high density macintosh format disks. 3-inch diskettes: Amstrad cpc, oric, pcw, spectrum, etc. Edit hitachi was a manufacturer of 3-inch disk drives, and stated in advertisements, "It's clear that the 3" floppy will become the new standard." 4 The format is widely used by Amstrad cpc and Amstrad pcw machines, became available for Spectrum systems once Amstrad took. Three-inch diskettes bear much similarity to the 3-inch size, but with some unique features. One example is the more elongated plastic casing, taller than a 3-inch disk, but less wide and thicker (i.e. The actual 3-inch magnetic-coated disk occupies less than 50 of the space inside the casing, the rest being used by the complex protection and sealing mechanisms implemented on the disks, which thus are largely responsible for the thickness, length, and relatively high costs of the. On the early Amstrad machines (the cpc line and the pcw 8256 the disks are typically flipped over to change the side (acting like 2 separate single-sided disks, comparable to the "flippy disks" of 5-inch media) as opposed to being contiguously double-sided. Double-sided mechanisms were introduced on the later pcw 85, thus removing the need to remove, flip, and then reinsert the disk.
Post-1991 machines including the A5000 and Risc pc add support for high-density disks with F format, storing 1600 KB. However, the pc combo io chips used are unable to format disks with sector skew, losing some performance. Adfs and the pc controllers also support extra-high density (ED) disks as G format, storing 3200 kb, but ed drives were never fitted to production machines. With risc os 3, the Archimedes can also read and write disk formats from other machines (for example the Atari st and the ibm pc, which are largely compatible depending on the st's os version). With third-party software it can even read the bbc micro's original single-density 5-inch dfs disks. The Amiga's disks cannot way be read by this system as they omitted the usual sector gap markers. The Acorn filesystem design is interesting to some people because all adfs-based storage devices connect to a module called FileCore which provides almost all the features required to implement an adfs-compatible filesystem. Because of this modular design, it is easy in risc os 3 to add support for so-called image filing systems.
Adfs also stores some metadata about each file, notably a load address, an execution address, owner and public privileges, and a lock bit. Even on the eight-bit machines, load addresses are stored in 32-bit format, since those machines support 16- and 32-bit coprocessors. The adfs format was later adopted into the bbc line upon release of the bbc master. The bbc master Compact marked the move to 3-inch disks, using the same adfs formats. The Acorn Archimedes adds D format, which increases the number of objects per directory from 44 to 77 and increase the storage space to 800 KB. The extra space is obtained by using 1024 byte sectors instead of the usual 512 bytes, thus reducing the space needed for inter-sector gaps. As a further enhancement, successive tracks are offset by a sector, giving time for the head to advance to the next track without missing the first sector, thus increasing bulk throughput. The Archimedes uses special values in the adfs load/execute address metadata to store a 12-bit filetype field and a 40-bit timestamp. Risc os 2 introduces E format, which retaines the same physical layout as D format, but supports file fragmentation and auto-compaction.
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The purpose is to detect disk changes, and various utilities such as Noclick exist that can disable the clicking noise to the relief of many Amiga users. Citation needed Acorn Electron, bbc micro, and Acorn Archimedes edit The British company Acorn Computers used non-standard disk formats in their 8-bit bbc micro and Acorn Electron, and their successor the 32-bit Acorn Archimedes. Acorn however, used standard disk controllers: initially fm, though they quickly transitioned to mfm. The original disk implementation for the bbc micro stores 100 kb (40 track) or 200 kb (80 track) per side on 5-inch disks in a custom format using the disc Filing System (DFS). Due to the incompatibility between 40- and 80-track drives, much software was notary distributed on combined 40/80-track disks. These work by writing the same data in pairs of consecutive tracks in 80-track format, and including a small loader program on track 1 (which is in the same physical position in either format). The loader program detects which type of drive is in use, and loads the main software program straight from disk bypassing the dfs, double-stepping for 80-track drives and single-stepping for 40-track.
This effectively achieves downgraded capacity to 100 KB from either disk format, but enabled distributed software to be effectively compatible with either drive. For their Electron floppy-disk add-on, Acorn chose 3-inch disks and developed the Advanced Disk filing System (adfs). It uses double-density recording and adds the ability to treat both sides of the disk as a single disk. This offers three formats: S (small 160 kb, 40-track single-sided; M (medium 320 kb, 80-track single-sided; L (large 640 kb, 80-track double-sided. Adfs provides hierarchical directory structure, rather than the flat model of dfs.
On the pc, however, there is no way to read an Amiga disk without special hardware, such as a catWeasel, and a second floppy drive. 2 Commodore never upgraded the Amiga chip set to support high-density floppies, but sold a custom drive (made by Chinon) that spins at half speed (150 rpm ) when a high-density floppy was inserted, enabling the existing floppy controller to be used. This drive was introduced with the launch of the Amiga 4000, although the later Amiga 1200 was only fitted with the standard dd drive. The Amiga hd disks can handle 1760 kb, but using special software programs they can hold even more data. A company named Kolff Computer Supplies also made an external hd floppy drive (kcs dual hd drive) available which can handle hd format diskettes on all Amiga computer systems. 3 Because of storage reasons, the use of emulators and preserving data, many disks were packed into disk images.
Currently popular formats are. Adf ( Amiga disk file. Dms ( DiskMasher ) and. Ipf ( Interchangeable Preservation Format ) files. The diskMasher format is copy-protected and has problems storing particular sequences of bits due to bugs in the compression algorithm, but was widely used in the pirate and demo scenes. Adf has been around for almost as long as the Amiga itself though it was not initially called by that name. Only with the advent of the internet and Amiga emulators has it become a popular way of distributing disk images. The proprietary ipf files were created to allow preservation of commercial games which have copy protection, which is something that adf and dms cannot. The Amiga is also notorious for the clicking sound made by the floppy drive mechanism if no disk is inserted.
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Under the Atari dos scheme, sector 360 is the fat sector map, and sectors 361-367 gpa contain the file listing. The Atari-brand dos versions and compatible use three bytes per sector for housekeeping and to link-list to the next sector. Third-party dos systems added features such as double-sided drives, subdirectories, and drive types such.2 mb and 8-inch. Well-known internet 3rd party Atari dos products include Smartdos (distributed with the rana disk drive topDos, mydos and Spartados. Commodore Amiga edit The pictured chip, codenamed paula, controls floppy access on all revisions of the commodore Amiga as one of its many functions The commodore Amiga computers use an 880 KB format (11512-byte sectors per track, times 80 tracks, times two sides) on a 3-inch. Because the entire track is written at once, intersector gaps can be eliminated, saving space. The Amiga floppy controller is basic but much more flexible than the one on the pc: it is free of arbitrary format restrictions, encoding such as mfm and gcr can be done in software, and developers were able to create their own proprietary disk formats. Because of this, foreign formats such as the ibm pc -compatible can be handled with ease (by use of Crossdos, which was included with later versions of Amigaos ). With the correct filesystem driver, an Amiga can theoretically read any arbitrary format on the 3-inch floppy, including those recorded at a slightly different rotation rate.
Later dos versions (3.0 and later.5) and doses by third parties (i.e. Oss) accept (and format) disks with up to 9ectors, resulting in 127 kb of storage capacity per disk side on drives equipped with double-density heads (. Not the Atari 810). That unusual 127 KB format allows sectors 1-720 to still be read on a single-density 810 disk drive, and was introduced by Atari with the 1050 drive with the introduction of dos.0 in 1983. A true 180K double-density Atari floppy format uses 128-byte sectors for sectors 1-3, then 256-byte sectors for 4-720. The first three sectors typically contain boot code as used by the onboard rom os; it is up to the resulting boot program (such as Spartados) to recognize the density of the formatted disk structure. While this 180K format was developed by Atari for their dos.0D and their (canceled) Atari 815 floppy drive, that double-density dos was never widely released and the format was generally goodall used by third-party dos products.
operating system uses a disk format that is largely identical to the commodore dos format with a few minor extensions; while generally compatible with standard Commodore disks, certain disk maintenance operations can corrupt the filesystem without proper supervision from the geos kernel. Atari 8-bit line edit The combination of dos and hardware (810, 1050 and XF551 disk drives) for Atari 8-bit floppy usage allows sectors numbered from 1 to 720. The dos's.0 disk bitmap provides information on sector allocation, counts from 0 to 719. As a result, sector 720 cannot be written to by the dos. Some companies used a copy-protection scheme where hidden data was put in sector 720 that cannot be copied through the dos copy option. Another more-common early copy-protected scheme simply does not record important sectors as allocated in the fat, so the dos utility package (DUP) does not duplicate them. All of these early techniques were thwarted by the first program that simply duplicated all 720 sectors.
Group Coded Recording (GCR) scheme used in 1541 and compatibles employed four different data rates depending upon track position (see zone bit recording ). Tracks 1 to 17 had 21 sectors, 18 to 24 had 19, 25 to 30 had 18, and 31 to 35 had 17, for a disk capacity of 170.75 KB (175 decimal kB). Unique among personal computer architectures, the operating system on the computer itself is unaware of the details of the disk and filesystem; disk operations are handled. Commodore dos instead, which was implemented using with an extra. Mos-6502 processor on the disk drive. Many programs such as geos bypass Commodore's dos completely, and replace it with fast-loading (for the time) programs in the 1541 drive. Eventually commodore gave in to disk format standardization, and made its last 5-inch drives, the 15, compatible with Modified Frequency modulation (mfm to enable the commodore 128 to work with CP/M disks from several vendors. Equipped with one of these drives, the C128 is able to access both C64 and CP/M disks, as it needs to, as well as ms-dos disks (using third-party software which was a crucial feature for some office work.
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For the msd floppy drive, see. A 3" floppy disk by Amstrad. This format was used by their cpc and Spectrum lines and in some systems by other manufacturers. The floppy disk is a ubiquitous data storage and transfer device from the mid-1970s write well into the 2000s. 1, besides the 3-inch and 5-inch formats used. Ibm pc compatible systems, or the 8-inch format that preceded them, many proprietary floppy disk formats were developed, either using a different disk design or special layout and encoding methods for the data held on the disk. Contents 1 Commodore 64/128 2 Atari 8-bit line 3 Commodore Amiga 4 Acorn Electron, bbc micro, and Acorn Archimedes 5 3-inch diskettes: Amstrad cpc, oric, pcw, spectrum, etc. 6 ibm demiDiskettes 7 Flippy disks 8 Auto-loaders 9 Floppy mass storage 10 2-inch floppy disks 11 Standard floppy replacements 12 see also 13 References 14 Bibliography 15 External links, commodore 64/128 edit, commodore started its tradition of special disk formats with the 5-inch disk. Pet/cbm, vic-20 and, commodore 64 home computers, the same as the 15rives used with the later two machines.