The Amiga 500, also called the A500, was the first widely used version of the Amiga home computer. It uses the same Motorola 68000 processor as the Amiga 1000, along with the same graphics and sound chips, but has a smaller case similar to the Commodore 128. Released in 1987, the Amiga 500 was the first home computer that could run multiple tasks at the same time. It also had colorful graphics, which was better than most high-end computers like the IBM PC and the original Macintosh, which had limited color or no color at all.

Commodore introduced the Amiga 500 at the January 1987 Consumer Electronics Show, at the same time as the more advanced Amiga 2000. It first sold in the Netherlands in April 1987, then in other parts of Europe in May. In North America and the UK, it became available in October 1987 with a price of $699 or £499. It directly competed with models from the Atari ST series.

The Amiga 500 was sold in the same stores as the Commodore 64, unlike the Amiga 1000, which was only sold in computer stores. It became Commodore’s most successful model, especially in Europe. While it was popular among hobbyists, it was most widely used as a gaming machine because its graphics and sound were much better than other computers at the time. A newer version, the Amiga 500 Plus, was later released, and the 500 series stopped being sold in 1992.

Releases

In mid-1988, the price of the Amiga 500 was lowered from £499 to £399. Later, from October 1989 to September 1990, the Amiga 500 was sold with the Batman Pack in the United Kingdom. This bundle included the games Batman, F/A-18 Interceptor, The New Zealand Story, and the bitmap graphics editor Deluxe Paint 2. It also included the Amiga video connector, which allowed the A500 to be used with a standard CRT television.

In November 1991, the improved Amiga 500 Plus replaced the original Amiga 500 in some markets. In the United Kingdom, it was sold with the Cartoon Classics pack for £399, though many stores still labeled it as an "A500." The Amiga 500 Plus was very similar to the original A500, except it had a new operating system, 1MB of Chip memory, a different "trap-door" expansion slot, and a slightly redesigned keyboard. In mid-1992, both the A500 and A500 Plus were discontinued and replaced by the Amiga 600. In late 1992, Commodore released the Amiga 1200, a computer closer in design to the original Amiga 500 but with major technical upgrades. However, neither the A1200 nor the A600 achieved the same level of commercial success as the original Amiga 500. By this time, the home computer market had largely shifted to IBM PC-compatible systems with VGA graphics and low-cost Macintosh models such as the Classic, LC, and IIsi.

Description

The Amiga 500 looks similar to the Commodore 128 and was called "Rock Lobster" during development. It has a keyboard and a central processing unit (CPU) in one unit, unlike the Amiga 1000. The keyboard on Amiga 500 computers sold in the United States has 94 keys, including 10 function keys, 4 cursor keys, and a number pad. European versions have two extra keys, except for the British version, which still has 94 keys. The computer uses a Motorola 68000 microprocessor that runs at 7.159 09 MHz in NTSC regions and 7.093 79 MHz in PAL regions. The CPU uses a 32-bit model with 32-bit registers. However, it has a 16-bit main arithmetic logic unit (ALU), a 16-bit external data bus, and a 24-bit address bus, allowing up to 16 MB of memory. A 3 + 1⁄2-inch floppy disk drive is built into the base of the computer. Up to three external floppy drives, either 3 + 1⁄2- or 5 + 1⁄4-inch, can be added through the disk drive port. Additional drives are connected by linking them in a chain. These drives support double-sided disks with a capacity of 901,120 bytes, as well as 360- and 720-KB disks formatted for IBM PC compatibles.

The earliest Amiga 500 models use the same Original Amiga chipset as the Amiga 1000. This allows the computer to display graphics in multiple resolutions and color depths on the same screen. For NTSC regions, resolutions range from 320×200 (up to 32 colors) to 640×400 (up to 16 colors), with an overscan resolution of 704×484. For PAL regions, resolutions range from 320×256 to 640×512, with an overscan resolution of 704×576. The system uses planar graphics, with up to five bitplanes (four in high resolution), enabling 2-, 4-, 8-, 16-, and 32-color screens from a palette of 4096 colors. Two special graphics modes are available: Extra HalfBrite, which uses a sixth bitplane to reduce pixel brightness by half, and Hold-And-Modify (HAM), which allows all 4096 colors to appear on screen at once. Later versions of the chipset can switch between NTSC and PAL settings in software.

The sound chip produces four mixed audio channels, two for the left speaker and two for the right speaker, using 8-bit PCM with a sampling frequency up to 28 kHz. Each channel has its own volume and sampling rate, and can be linked to another channel to adjust volume and frequency. If direct memory access (DMA) is disabled, the sampling frequency can reach 56 kHz. A common technique allows 14-bit precision sound output, enabling 14-bit 56 kHz audio.

The Amiga 500 comes with AmigaOS version 1.2 or 1.3 and 512 KB of chip RAM (150 ns access time). It includes a built-in double-density floppy disk drive that can read 720 KB IBM PC disks, 880 KB standard Amiga disks, and up to 984 KB with custom formatting.

Although the Amiga 500 lacks internal expansion slots compatible with the Amiga 2000, it offers many ports and expansion options. It has two Atari joystick ports for joysticks or mice, stereo audio RCA connectors, and a floppy drive port for connecting up to three external floppy drives. It also includes an RS-232 serial port and a Centronics parallel port. The power supply provides +5 V and ±12 V. Video output uses

Technical specifications

The computer uses either an OCS (1.2 and 1.3 models) or ECS (1.3 and 500+ 2.04 models) chipset. The ECS chipset allows users to switch between PAL and NTSC video modes using software. The sound system has four hardware channels that produce 8-bit audio up to 28 kHz. Each channel has its own volume (65 levels) and sampling rate, and they combine into two stereo outputs (left and right). A low-pass audio filter can be controlled through software.

The computer has 512 KB of chip RAM with a 150 ns access time. It runs AmigaOS 1.2 or 1.3, which can be upgraded to version 3.1.4 if 2 MB of RAM is installed. A built-in 3.5" double-density floppy disk drive can read 720 KB IBM PC disks, 880 KB Amiga disks, or up to 984 KB with custom formatting. It uses 300 rpm and 250 kbit/s. The computer includes a built-in keyboard and a two-button mouse.

In PAL mode, the maximum resolution is 768×580 (overscan interlaced on composite monitors/TVs). Common resolutions include 320×256, 640×256, or 640×512 (all with borders). In NTSC mode, the maximum resolution is 768×484 (overscan interlaced on composite monitors/TVs). Common resolutions include 320×200, 640×200, or 640×400 (all with borders). Graphics can be displayed in any size, resolution, or color depth, even on the same screen. The computer can show multiple resolutions at once, splitting the screen vertically.

Planar graphics use up to five bitplanes (four in high-resolution mode), allowing screens with 2, 4, 8, 16, or 32 colors from a palette of 4096 colors. Two special graphics modes are available: Extra Half Brite (EHB), which uses a sixth bitplane to reduce brightness, and Hold-And-Modify (HAM), which allows all 4096 colors on screen at once. HAM uses 12 bits per pixel over a 3-pixel span by modifying one color component from the previous pixel. This can cause minor color artifacts.

The A500 can have up to 138 MB of total RAM: 2 MB chip RAM, 8 MB 16-bit fast RAM, and 128 MB 32-bit fast RAM. The original 512 KB chip RAM can be expanded using a "trapdoor" slot (A501 or compatible). However, early versions of the Agnus chip limited this memory to "Slow RAM" or "Pseudo-fast RAM," as it could not be used as chip RAM. Later ECS Agnus versions allowed trapdoor memory to be used as chip RAM, increasing total chip RAM to 1 MB.

Third-party expansions can add up to 2 MB of trapdoor memory. A Gary adapter can map this memory as split chip RAM and slow RAM or fully as slow RAM. Using an A3000 Agnus on an adapter board, chip RAM can be expanded to 2 MB, matching the A500+.

"Fast RAM" connects to the CPU-side bus and is only accessed by the CPU. It is not slowed by chipset activity. The side expansion port supports up to 8 MB of Zorro-style RAM. A CPU adapter allows internal expansion. Internal or external CPU accelerators may include their own RAM. 16-bit CPUs are limited by 24-bit addressing but can use unused memory space for RAM. 32-bit CPUs are not limited by 24-bit addressing and can include up to 128 MB of fast RAM.

The computer has two Atari joystick ports, stereo audio RCA connectors, a floppy drive port (DB23F) for daisy-chaining up to three extra floppy drives, an RS-232 serial port (DB25M), a parallel port (DB25F), a power inlet (+5 V, ±12 V), and an Amiga-specific DB23 M connector for analogue RGB video output (50 Hz PAL, 60 Hz NTSC). It can drive video with 15.75 kHz HSync but is not compatible with most VGA monitors. A multisync monitor is needed for higher resolutions. The connector also supports genlocking to external video signals. An RF adapter (A520) was often included for TV or composite monitor output. A digital 16-color RGBI signal is also available on the same connector. A monochrome video output is provided via an RCA connector. A Zorro II bus expansion slot is on the left side, and a trapdoor slot is under the machine for RAM expansion and a real-time clock.

Expansion options are limited to a side expansion port and a trapdoor slot. The casing can be opened (voiding the warranty), and larger chips are socketed for replacement. The CPU can be upgraded to a Motorola 68010 directly or to a 68020, 68030, or 68040 via the side expansion slot or a CPU socket adapter. Chip RAM can be upgraded to 1 MB with a Fat Agnus chip installed. All custom chips can be upgraded to the ECS chipset. The A500+ model allows 1 MB trapdoor chip RAM upgrades without a clock, but some programs may not work due to compatibility issues. Modification instructions exist to add 512 KB RAM to the motherboard and extend address lines to the trapdoor slot for additional RAM. Up to 8 MB of fast RAM can be added via the side expansion slot, and more with a non-EC processor and 32-bit RAM. Hard drives and peripherals can also be added through the side expansion slot. Companies offered combined CPU, memory, and hard drive upgrades or chainable expansions that extended the bus. Expansions are automatically configured by AutoConfig software, preventing hardware conflicts.

When powered on, the computer runs a self-diagnostic test indicated by specific colors:
1. Medium green: Chip RAM not found or damaged.
2. Red: Bad kickstart ROM.
3. Yellow: CPU crash or bad Zorro expansion card.
4. Blue: Custom chip problem (Denise, Paula, or Agnus).
5. Light green: CIA problem.
6

Trap-door expansion 501

The Amiga 500 computer could be upgraded with the Amiga 501 circuit board, which is installed underneath the computer and covered by a plastic panel. This upgrade includes 512 KB of RAM, which is set to "Slow RAM" or "trap-door RAM" by default. It also includes a real-time clock (RTC) that uses a battery to keep track of time even when the computer is turned off.

The 512 KB of trap-door RAM added by the Amiga 501, combined with the original 512 KB of chip RAM in the Amiga 500, creates a total of 1 MB of memory. The trap-door RAM is called "Slow RAM" because the computer's main chip cannot access it quickly due to shared data pathways.

Later versions of the Amiga 500 motherboard included special connections that allowed the trap-door RAM to be used as chip memory, but only if the Agnus chip was the newer ECS version found in later models. The latest version of the Amiga 500 (rev 8) shared its motherboard with the Amiga 500+ and set the added memory as chip memory by default.

Software

Every time the Amiga 500 is turned on, it runs instructions stored in the Kickstart ROM. The Amiga 500 originally came with AmigaOS 1.2, but models produced from October 1988 onward included AmigaOS 1.3 instead.

Reception and sales

The Amiga 500 was the most popular computer in the Amiga family. A German computer magazine called Chip gave the Amiga 500 the "Home Computer of the Year" award three years in a row. At the European Computer Trade Show in 1991, the Amiga 500 also received the Leisure Award for a similar "Home Computer of the Year" title.

Because the Amiga 500 was affordable in Europe during the 1990s, sales of the Amiga family were strongest there. In the fourth quarter of 1990, Europe made up 85 percent of Commodore's total sales. The Amiga 500 was often seen as a gaming computer, while the Amiga 2000 was used more by artists and hobbyists.

Some people say Commodore sold as many as six million Amiga computers worldwide. However, Commodore UK disagreed and stated that all Amiga models sold between four and five million units. Ars Technica provides a graph showing the yearly sales of all Amiga computers.

The Amiga 500 sold 1,160,500 units in Germany, including sales of the Amiga 500 Plus model.

Amiga 500 Plus

The Amiga 500 Plus (also called A500 Plus or A500+) is an updated version of the original Amiga 500 computer. The A500+ had small changes to its main circuit board, making it less expensive to produce than the original A500. It was known for including new versions of Kickstart and Workbench, as well as minor improvements to the custom chips, called the Enhanced Chip Set (ECS).

Although officially released in 1992, some Amiga 500 computers sold in late 1991 already had the updated motherboard used in the A500+. While the A500+ was an improvement over the original A500, the changes were small. It was later replaced by the Amiga 600 in summer 1992, making it the Amiga model that was used for the shortest time.

Because of the new Kickstart version 2.04, several popular games, such as Treasure Island Dizzy, Lotus Esprit Turbo Challenge, and SWIV, did not work on the A500+. Some users returned these games to stores, asking for the original Kickstart 1.3 version of the Amiga 500. This problem was later fixed by third-party companies that created boards allowing the A500+ to use Kickstart 1.2 or 1.3. It also encouraged game developers to improve their programming methods, which was important because Commodore planned to release the next-generation Amiga 1200 computer. A program called Relokick (included in an issue of CU Amiga) allowed the A500+ to load a Kickstart 1.3 ROM image into memory, enabling most incompatible software to run. However, this used 512 KB of system memory, causing some 1 MB games to fail due to lack of available memory. Later, updated versions of some games were released, such as budget editions of Lotus 1 and SWIV, and an updated version of Bubble Bobble. Double Dragon 2 by Binary Design received an update for ECS machines, fixing graphics issues and reducing loading times from about 20 seconds to just over 6 seconds.

• Motorola 68000 CPU running at 7.09 MHz (PAL) / 7.16 MHz (NTSC), like its predecessor
• 1 MB of Chip RAM (very early versions had 512 KB)
• Kickstart 2.04 (v37.175)
• Workbench 37.67 (release 2.04)
• Built-in battery-powered real-time clock (RTC)
• Full ECS chipset, including a new version of the Agnus chip and Denise chip