Music Amiga Promotion "Gateway-1999"

***AMIGA 500***

Manufacturer: Commodore International
Type: Home computer
Release date: 1987
Discontinued: 1991
Media: 880 KB floppy disks
Operating system: AmigaOS 1.2~1.3
CPU: Motorola 68000 @ 7.16 MHz (NTSC) - 7.09 MHz (PAL)
Memory: 512 KB (9.5 MB maximum)
Graphics: 640 x 256, 6 bpp @ 25 fps
Predecessor: Amiga 1000
Successor: Amiga 500 Plus


The Amiga 500, also known as the A500 (or its code name 'Rock Lobster'),was the first low-end Commodore Amiga 16/32-bit multimedia home/personal computer. It was announced at the winter Consumer Electronics Show in January 1987, at the same time as the high-end Amiga 2000, and competed directly against the Atari 520ST. The A500 was released in mid 1987 at the price of 595.95 USD without monitor. The 500 represented a return to Commodore's roots, being sold in the same mass retail outlets as the Commodore 64 to which it was a spiritual successor, as opposed to the computer store-only Amiga 1000.
The original A500 proved to be Commodores best-selling Amiga model, enjoying particular success in Europe.Although popular with hobbyists, arguably its most widespread use was as a gaming machine, where its advanced graphics and sound for the time were of significant benefit.
Like its predecessor, the Amiga 500 uses a Motorola 68000 microprocessor running at 7.15909 MHz in the NTSC version or 7.09379 MHz in the PAL version. While the 68000 is a 32-bit chip internally, it has a 16-bit data bus and 24-bit address bus, providing a maximum of 16 MB address space. Also like the Amiga 1000, the 500 uses the OCS chipset. Graphics can be of arbitrary dimensions, resolution and colour depth, even on the same screen. Without using overscan, the graphics can be 320 or 640 pixels wide by 200 (NTSC standard) /256 (PAL standard) or 400 (NTSC interlace)/512 (PAL interlace mode) pixels tall. Overscan mode enabled 700 x 600 resolution in PAL machines.Planar graphics are used, with up to 5 bitplanes (4 in hires), allowing 2, 4, 8, 16 and 32 colour screens, from a palette of 4096 colours. Two special graphics modes were also included: Extra HalfBrite, which used a 6th bitplane as a mask that halved the brightness of any colour seen, and Hold And Modify (HAM), which allowed all 4096 colours on screen at once. Later revisions of the chipset made PAL/NTSC mode switchable in software.
Sound is 4 hardware-mixed channels of 8-bit PCM sound at up to 28 kHz. The hardware channels had independent volumes (65 levels) and sampling rates, and mixed down to two fully left and fully right stereo outputs. Each channel is designated another channel for which it can optionally modulate both volume and frequency using its own output. A software controllable low-pass audio filter is also included. The machine came standard with 512 KB of Chip RAM and AmigaOS 1.2 or 1.3. One double-density floppy disk drive is included, which is completely programmable and thus can read 720 KB IBM PC disks, 880 KB standard Amiga disks, and up to 984 KB with custom formatting (such as Klaus Deppichs diskspare.device). Breaking with the Amiga 1000, and in keeping with the home computer tradition established by the VIC-20 and C64, the A500 had its keyboard integrated with the CPU unit, although the floppy disk drive is also integrated, unlike the 8-bit models. The 500 used the standard Amiga two-button mouse.
Despite the lack of Amiga 2000-compatible internal expansion slots, there are many ports and expansion options. There are two Atari 2600 DE9M sockets for joysticks or mice, stereo audio (RCA connectors 1V p-p). There is a floppy drive port for daisy-chaining up to 3 extra floppy disk drives via an DB23F connector.The then-standard RS-232 serial port (DB25M) and Centronics parallel port (DB25F) is also included. The power supply is (+5 V , +/-12 V).The Amiga 500's graphics are output in analogue RGB 50 Hz PAL and 60 Hz NTSC video output, provided on an Amiga-specific DB23M video connector. It can drive video with 15,75 kHz HSync for standard Amiga video modes but this is not compatible with most VGA monitors. A Multisync monitor is required for some higher resolutions. This connection can also be genlocked to an external video signal. An RF adapter was bundled with the machine to provide output on regular televisions. Monochrome video is available via an RCA connector. There is a Zorro II bus expansion the left side behind a plastic cover and a trapdoor slot under the machine, for RAM expansion and real-time clock.