MFM

The Apple II, one of the very first personal computers, is widely seen as the founding pioneer and literal grandfather of the personal computer industry of today. As the direct descendant of the Apple I, it evolved from a meager hand-built computer kit intended for hobbyist, to a fully factory assembled machine ready-to-use out of the box most anyone could use. With its elegant case styling and simplicity (requiring just a television set as a display) it represented a computer that for the first time c ...

Including:

• Apple II family - History
• Apple II family - The original Apple II
• Apple II family - The family grows
• Apple II family - Apple II Plus
• Apple II family - Apple IIe
• Apple II family - Apple IIc
• Apple II family - Apple IIGS
• Apple II family - Apple IIc Plus
• Apple II family - Apple IIe Card
• Apple II family - The Final Years
• Apple II family - Clones
• Apple II family - General
• Apple II family - Apple II media
• Apple II family - Different style renditions of the II name
• Apple II family - Life after death
• Apple II family - Industry impact

Read more here: » Apple II family: Encyclopedia - Apple II family

Amiga uses MFM encoding/decoding by default when handling floppy disks. There are 80 cylinders on an Amiga floppy disk. Each cylinder has 2 MFM tracks, 1 on each side of the disk. Double density (DD) disks have 11 sectors per MFM track, High density (HD) disks have 22 sectors. The geometry of an Amiga Floppy Disk is as follows: DD disks: 512 bytes/sector, 11 sector/track, 2 track/cyl, 80 cyl/disk HD disks: 512 bytes/sector, 22 sector/track, 2 track/cyl, 80 cyl/disk The DD disk has 11 * 2 * 80 = 1760 (0 to 1759) ...

See also:

Amiga Old File System, Amiga Old File System - History, Amiga Old File System - Characteristics

Read more here: » Amiga Old File System: Encyclopedia II - Amiga Old File System - Characteristics

A hard disk uses rigid rotating platters (disks). Each platter has a planar magnetic surface on which digital data may be stored. Information is written to the disk by transmitting an electromagnetic flux through an antenna or read-write head that is very close to a magnetic material, which in turn changes its polarization due to the flux. The information can be read by a read-write head which senses electrical change as the magnetic fields pass by in ...

See also:

Hard disk, Hard disk - Mechanics, Hard disk - Access and interfaces, Hard disk - Other characteristics, Hard disk - Addressing modes, Hard disk - Manufacturers, Hard disk - Firms that have come and gone, Hard disk - Marketing capacity versus true capacity, Hard disk - Hard disk usage, Hard disk - History, Hard disk - Timeline of capacity and other technical improvements, Hard disk - 1950s, Hard disk - 1960s, Hard disk - 1970s, Hard disk - 1980s, Hard disk - 1990s, Hard disk - 2000s, Hard disk - Derivative technologies

Read more here: » Hard disk: Encyclopedia II - Hard disk - Mechanics

All CPC models were based on a Zilog Z80 processor clocked at 4 MHz. Because a common pool of RAM is shared with the video circuits, the Z80 may only make a memory accesses every four cycles - which has the effect of rounding all instruction cycle lengths up to the next multiple of four. The system came with 64 KB or 128 KB of RAM depending on the model (capable of being expanded to 512k). The machines also featured a standard 9-pin Atari-style joystick socket which was able to take two joysticks via a splitter.

See also:

Amstrad CPC, Amstrad CPC - The Amstrad CPC sold as a complete system, Amstrad CPC - The CPC family, Amstrad CPC - The Amstrad CPC 464 472 664 6128, Amstrad CPC - West Germany: Schneider CPC 464 664 and 6128, Amstrad CPC - East Germany: KC compact, Amstrad CPC - The CPC 5512, Amstrad CPC - PLUS models, Amstrad CPC - Hardware description, Amstrad CPC - Video graphics: modes outputs, Amstrad CPC - Audio sound, Amstrad CPC - The 3 floppy disk drives, Amstrad CPC - Serial port adaptor, Amstrad CPC - Similarities to the BBC Micro, Amstrad CPC - Software, Amstrad CPC - Built-in BASIC and operating system, Amstrad CPC - Other languages, Amstrad CPC - Criticism of CPC software games, Amstrad CPC - Notable games with screenshots, Amstrad CPC - Magazines, Amstrad CPC - The Amstrad CPC vs. its competitors, Amstrad CPC - Later Amstrad, Amstrad CPC - Hardware tricks on the CPC series

Read more here: » Amstrad CPC: Encyclopedia II - Amstrad CPC - Hardware description

The 1541 used a bit-serial version of the IEEE-488 interface, the speedier parallel version of which was used on Commodore's earlier drives for the PET/CBM range of personal/business computers. To ensure a ready supply of inexpensive cabling for its home computer peripherals, Commodore chose standard DIN connectors for the serial interface. Disk drives and other peripherals such as printers were connected to the computer via a daisy-chain schem ...

See also:

Commodore 1541, Commodore 1541 - Introduction and early problems, Commodore 1541 - Versions and third-party clones, Commodore 1541 - The serial computer interface, Commodore 1541 - Copy protection by read error, Commodore 1541 - The drive head misalignment issue, Commodore 1541 - Commodore's successor products

Read more here: » Commodore 1541: Encyclopedia II - Commodore 1541 - The serial computer interface

Disk formatting - Low-level formatting. Warning: The below information on low-level formatting of floppy disks may be technically incorrect. The process is most easily seen with a standard 1.44MB PC floppy disk. Low-level formatting of the floppy normally writes 18 sectors of 512 bytes each on each of 160 tracks (80 on each side) of a floppy disk. That provides 1,474,560 bytes of storage on the floppy. This means that the actual storage capacity of the disk is 1.40625MB. (Sectors are actually larger ...

See also:

Disk formatting, Disk formatting - Formatting a floppy disk, Disk formatting - Low-level formatting, Disk formatting - High-level formatting, Disk formatting - Formatting a hard disk drive, Disk formatting - Low-level formatting

Read more here: » Disk formatting: Encyclopedia II - Disk formatting - Formatting a floppy disk

LBA is a particularly simple addressing scheme; blocks are simply located by an index, with the first block being LBA=0, the second LBA=1, and so on. The LBA scheme replaces earlier schemes which exposed the physical details of the storage device to the software of the operating system. Chief among these was the cylinder-head-sector (CHS) scheme, where blocks were addressed by means of a tuple which defined the cylinder, head, and sector at which they appeared on the hard disk. CHS didn't map well to devices other than hard disks (such as ta ...

See also:

Logical block addressing, Logical block addressing - The LBA scheme, Logical block addressing - LBA mapping and LUN virtualisation, Logical block addressing - LBA and ATA devices

Read more here: » Logical block addressing: Encyclopedia II - Logical block addressing - The LBA scheme

According to legend, the city was founded in 2333 BC as Wanggŏmsŏng (왕검성; 王儉城). It became a major city under the Go-Joseon Dynasty. Goguryeo moved its capital here in 427. The Tang Empire and Silla allied and defeated Goguryeo in 668. In 676 it was taken by Silla but left in the border between Silla and Balhae until the Goryeo dynasty, when the city was revived as Sŏgyŏng (서경; 西京; "Western Capital," although never actually a capital of Goryeo). It was the provincial capital of the P'yŏngan Province during the Joseon Dynasty, becoming provincial capital of South P'yŏngan Province from 1896 and ...

See also:

Pyongyang, Pyongyang - History, Pyongyang - Historic names, Pyongyang - Administrative divisions, Pyongyang - Landmarks, Pyongyang - Transportation, Pyongyang - Climate, Pyongyang - Sister cities, Pyongyang - Notes

Read more here: » Pyongyang: Encyclopedia II - Pyongyang - History

The first QIC tapes were the 5.875 in by 3.875 in Data Cartridge (DC) format with two internal belt-driven reels and a metal base. They were introduced in 1972 by 3M. The original QIC tape format standard was QIC-11, which was a four-track format giving 20 MB on a 450 ft DC300XL cartridge. Later DC formats included QIC-24 (nine-track, 45 MB or 60MB on a 450 or 600 ft (DC600A) cartridge respectively), QIC-120 (15-track, 125 MB on a DC600A), QIC-150 (18-track, 150 MB, DC6150 cartridge), and QIC-525 (26 ...

See also:

Quarter Inch Cartridge, Quarter Inch Cartridge - QIC, Quarter Inch Cartridge - Pros and cons, Quarter Inch Cartridge - Travan, Quarter Inch Cartridge - SLR, Quarter Inch Cartridge - QIC-Wide, Quarter Inch Cartridge - QIC-EX, Quarter Inch Cartridge - QIC-157

Read more here: » Quarter Inch Cartridge: Encyclopedia II - Quarter Inch Cartridge - QIC

A hard disk uses rigid rotating platters (disks). Each platter has a planar magnetic surface on which digital data may be stored. Information is written to the disk by transmitting an electromagnetic flux through an antenna or read-write head that is very close to a magnetic material, which in turn changes its polarization due to the flux. The information can be read by a read-write head which senses electrical change as the magnetic fields pass by in ...

See also:

Hard disk, Hard disk - Mechanics, Hard disk - Access and interfaces, Hard disk - Other characteristics, Hard disk - Addressing modes, Hard disk - Manufacturers, Hard disk - Firms that have come and gone, Hard disk - Marketing capacity versus true capacity, Hard disk - Hard disk usage, Hard disk - History, Hard disk - Timeline of capacity and other technical improvements, Hard disk - 1950s, Hard disk - 1960s, Hard disk - 1970s, Hard disk - 1980s, Hard disk - 1990s, Hard disk - 2000s

Read more here: » Hard disk: Encyclopedia II - Hard disk - Mechanics

The central aspect of the chipset's power is that all operations are synchronised with the output of the video beam. This includes access to the built-in RAM, which is known as chip RAM because the chipset has access to it. The CPU and other members of the chipset have to arbitrate for access with Agnus. From the perspective of system architecture, this is known as Direct Memory Access (DMA), and Agn ...

See also:

Original Amiga chipset, Original Amiga chipset - Overview of chips, Original Amiga chipset - Agnus, Original Amiga chipset - Blitter, Original Amiga chipset - Copper, Original Amiga chipset - Denise, Original Amiga chipset - External video timing, Original Amiga chipset - Video output, Original Amiga chipset - Paula, Original Amiga chipset - Audio features in general, Original Amiga chipset - Feature overview, Original Amiga chipset - Hardware registers, Original Amiga chipset - Audio state machines, Original Amiga chipset - Floppy disk controller, Original Amiga chipset - Serial port

Read more here: » Original Amiga chipset: Encyclopedia II - Original Amiga chipset - Agnus

Apple II family - Apple II Plus. The Apple II was eventually superseded by the Apple II Plus, which included the Applesoft BASIC programming language in ROM. This Microsoft-authored dialect of BASIC, which was previously available as an upgrade, supported floating-point arithmetic (albeit at a slower speed than Steve Wozniak's Integer BASIC) and became the standard BASIC dialect on the Apple. The Apple II Plus had a total of 48 kilobytes of RAM, expandable to 64 KB by means of the language card,< ...

See also:

Apple II family, Apple II family - History, Apple II family - The original Apple II, Apple II family - The family grows, Apple II family - Apple II Plus, Apple II family - Apple IIe, Apple II family - Apple IIc, Apple II family - Apple IIGS, Apple II family - Apple IIc Plus, Apple II family - Apple IIe Card, Apple II family - The Final Years, Apple II family - Clones, Apple II family - General, Apple II family - Apple II media, Apple II family - Different style renditions of the II name, Apple II family - Life after death, Apple II family - Industry impact

Read more here: » Apple II family: Encyclopedia II - Apple II family - The family grows

Most of the world's hard disks are now manufactured by just a handful of large firms: Seagate, Maxtor (now owned by Seagate), Western Digital, Samsung, and Hitachi, the former drive manufacturing division of IBM. Fujitsu continues to make specialist notebook and SCSI drives but exited the mass market in 2001. Toshiba is a major manufacturer of 2.5-inch and 1.8-inch notebook drives. Hard d ...

See also:

Hard disk, Hard disk - Mechanics, Hard disk - Access and interfaces, Hard disk - Other characteristics, Hard disk - Addressing modes, Hard disk - Manufacturers, Hard disk - Firms that have come and gone, Hard disk - Marketing capacity versus true capacity, Hard disk - Hard disk usage, Hard disk - History, Hard disk - Timeline of capacity and other technical improvements, Hard disk - 1950s, Hard disk - 1960s, Hard disk - 1970s, Hard disk - 1980s, Hard disk - 1990s, Hard disk - 2000s

Read more here: » Hard disk: Encyclopedia II - Hard disk - Manufacturers

The drive-head mechanism was notoriously easy to misalign, and had a tendency to make a 'machine-gun' rattle when out of alignment or when formatting a new disk. Some people even wrote code to vibrate the head at different frequencies to play simple tunes such as Amazing Grace. The most common cause of the 1541's drive head knocking and subsequent misalignment, however, was copy prevention schemes on commercial software. The main cause of the problem was that the disk drive itself did not feature any means of detecting when the ...

See also:

Commodore 1541, Commodore 1541 - Introduction and early problems, Commodore 1541 - Versions and third-party clones, Commodore 1541 - The serial computer interface, Commodore 1541 - Copy protection by read error, Commodore 1541 - The drive head misalignment issue, Commodore 1541 - Commodore's successor products

Read more here: » Commodore 1541: Encyclopedia II - Commodore 1541 - The drive head misalignment issue

Early copy prevention schemes deliberately introduced read errors on the disk, the software refusing to load unless the correct error message was returned. The general idea was that the inbuilt disk copy command was incapable of copying the errors. When one of these errors was encountered, the disk drive (as do all disk drives) would attempt one or more re-read attempts after first resetting the head to track zero. Few of these schemes had much deterrent effect, as various software companies soon release ...

See also:

Commodore 1541, Commodore 1541 - Introduction and early problems, Commodore 1541 - Versions and third-party clones, Commodore 1541 - The serial computer interface, Commodore 1541 - Copy protection by read error, Commodore 1541 - The drive head misalignment issue, Commodore 1541 - Commodore's successor products

Read more here: » Commodore 1541: Encyclopedia II - Commodore 1541 - Copy protection by read error

Hard disk - 1950s. 1956 - first commercial hard disk, the IBM 350 RAMAC disk drive, 5 megabyte. Hard disk - 1960s. Hard disk - 1970s. Hard disk - 1980s. 1980 - first 5.25-inch Winchester drive, the Shugart ST-506, 5 megabyte (CS) 1986 - Standardization of SCSI Hard disk - 1990s. 1991 - 100 megabyte hard drive (CS) 1994 - ATA-1 standardi ...

See also:

Hard disk, Hard disk - Mechanics, Hard disk - Access and interfaces, Hard disk - Other characteristics, Hard disk - Addressing modes, Hard disk - Manufacturers, Hard disk - Firms that have come and gone, Hard disk - Marketing capacity versus true capacity, Hard disk - Hard disk usage, Hard disk - History, Hard disk - Timeline of capacity and other technical improvements, Hard disk - 1950s, Hard disk - 1960s, Hard disk - 1970s, Hard disk - 1980s, Hard disk - 1990s, Hard disk - 2000s

Read more here: » Hard disk: Encyclopedia II - Hard disk - Timeline of capacity and other technical improvements

Using a belt drive means that the speed the belt was moved at was equal to the speed the tape would move at. This is in contrast to cassette tapes or DATs, which rely on spindles in the reels, and which vary tape speed as the amount of tape on the reels changes. It also means that no tension is ever put on the tape; the belt is in contact with both reels, so the tape should maintain a neutral tension at all times. The tape in a QIC is not physically attached to the reels; the belt drive combined with punched holes to indicate an end-o ...

See also:

Quarter Inch Cartridge, Quarter Inch Cartridge - QIC, Quarter Inch Cartridge - Pros and cons, Quarter Inch Cartridge - Travan, Quarter Inch Cartridge - SLR, Quarter Inch Cartridge - QIC-Wide, Quarter Inch Cartridge - QIC-EX, Quarter Inch Cartridge - QIC-157

Read more here: » Quarter Inch Cartridge: Encyclopedia II - Quarter Inch Cartridge - Pros and cons

Denise controls the video timings, but can also synchronise to an external video signal. Denise is programmed to fetch planar video data from 1 to 5 bitplanes and translate that into a colour lookup. The number of bitplanes is arbitrary, thus if 32 colours are not needed, 2, 4, 8 or 16 can be used instead. The number of bitplanes (and resolution) can be changed on the fly by the copper. This allows for very economical use of chip RAM. There is also a sixth bitplane, which can be used in special modes: Extra-HalfBrite (EHB) – i ...

See also:

Original Amiga chipset, Original Amiga chipset - Overview of chips, Original Amiga chipset - Agnus, Original Amiga chipset - Blitter, Original Amiga chipset - Copper, Original Amiga chipset - Denise, Original Amiga chipset - External video timing, Original Amiga chipset - Video output, Original Amiga chipset - Paula, Original Amiga chipset - Audio features in general, Original Amiga chipset - Feature overview, Original Amiga chipset - Hardware registers, Original Amiga chipset - Audio state machines, Original Amiga chipset - Floppy disk controller, Original Amiga chipset - Serial port

Read more here: » Original Amiga chipset: Encyclopedia II - Original Amiga chipset - Denise

There were two versions of the 1541 mechanics. Early models used a drive mechanism made by Alps Electric, distinguishable by its push-down drive door. Later models utilized a drive mechanism manufactured by Newtronics (Mitsumi), which used a lever release. All but the very earliest 1541s can use either the Alps or Newtronics mechanism. Visually, the first models, of the VIC-1541 denomination, had an off-white color like the VIC-20 and VIC-1540. Then, to match the look of the C64, CBM changed the d ...

See also:

Commodore 1541, Commodore 1541 - Introduction and early problems, Commodore 1541 - Versions and third-party clones, Commodore 1541 - The serial computer interface, Commodore 1541 - Copy protection by read error, Commodore 1541 - The drive head misalignment issue, Commodore 1541 - Commodore's successor products

Read more here: » Commodore 1541: Encyclopedia II - Commodore 1541 - Versions and third-party clones

The first hard disk drive was the IBM 350 Disk File, invented by Reynold Johnson and introduced in 1955 with the IBM 305 computer. This drive had fifty 24 inch platters, with a total capacity of five million characters. A single head was used for access to all the platters, making the average access time very slow. The IBM 1301 Disk Storage Unit, announced in 1961, introduced the usage of a separate head for each data surface. The first disk drive to use removable media was the IBM 1311 drive, which used the IBM 1316 disk ...

See also:

Hard disk, Hard disk - Mechanics, Hard disk - Access and interfaces, Hard disk - Other characteristics, Hard disk - Addressing modes, Hard disk - Manufacturers, Hard disk - Firms that have come and gone, Hard disk - Marketing capacity versus true capacity, Hard disk - Hard disk usage, Hard disk - History, Hard disk - Timeline of capacity and other technical improvements, Hard disk - 1950s, Hard disk - 1960s, Hard disk - 1970s, Hard disk - 1980s, Hard disk - 1990s, Hard disk - 2000s, Hard disk - Derivative technologies

Read more here: » Hard disk: Encyclopedia II - Hard disk - History