Amiga 500
 | |
| Amiga 500 with monitor, external floppy drive and mouse | |
| Specifications | |
|---|---|
| Manufacturer | Commodore |
| Type | Home computer |
| Released | April 1987 (Netherlands); October 1987 (North America and UK)[1] |
| Intro price | US$699 / £499[1] |
| CPU | Motorola MC68000; 7.09379 MHz (PAL), 7.15909 MHz (NTSC)[2][1] |
| Memory | 512 KB, expandable to 1 MB[2] |
| Storage | Internal 3.5-inch double-sided double-density drive, 880 KB per disk[2] |
| Display | — |
| Sound | Paula 8364, two stereo audio outputs[2] |
| Graphics | Agnus (8370/8371, or 8372 on Rev. 6A/7) and Denise 8362[2] |
| ROM | Kickstart 1.3, 256K × 16 at U6[2] |
| Ports / interface | RS-232 serial, Centronics parallel, external disk, two mouse and game ports, RGB and composite video, stereo audio, keyboard, memory cartridge (trapdoor) and expansion edge[2] |
| Power | External supply 312503-01: +5 V 4.3 A, +12 V 1.0 A, −12 V 0.1 A[2] |
| OS / Firmware | Kickstart and Workbench[2] |
| Successor | Amiga 600 |
The Amiga 500 (A500) is a 16-bit home computer made by Commodore. It went on sale in the Netherlands in April 1987 and in North America and the UK in October 1987, at a list price of US$699 or £499.[1] The keyboard, main board and a 3.5-inch floppy drive share one case, and the power supply is an external brick. Commodore's service manual gives 512 KB of RAM, expandable to 1 MB with a memory cartridge in the trapdoor under the machine.[2]
Specification
[edit | edit source]| Item | Specification |
|---|---|
| Processor | Motorola MC68000 |
| Memory | 512 KB, expandable to 1 MB |
| Disks | 3.5-inch double-sided double-density, 880 KB formatted |
| Mouse | Mechanical, 200 counts per inch |
| Interfaces | RS-232 serial, Centronics parallel, external disk, mouse and game ports, keyboard, two audio outputs, memory cartridge, expansion |
| Monitors | Analogue RGB, digital RGB, monochrome (composite video) and standard televisions |
| Operating temperature | 5 to 40 °C |
The 68000 runs at 7.09379 MHz on PAL machines and 7.15909 MHz on NTSC machines.[1] Commodore's troubleshooting section expects a 7 MHz clock at pin 15 of the 68000, about 3.58 MHz on the CCK and CCKQ lines, and 28 MHz at pin 34 of Agnus.[2]
Main board
[edit | edit source]Chips
[edit | edit source]| Position | Rev. 5 | Rev. 6A/7 |
|---|---|---|
| U1 | MC68000, 390084-03 | MC68000 |
| U2 | Fat Agnus 8370 R3 (NTSC, 318070-01) or 8371 R1 (PAL, 318071-01) | 8372 R3 Agnus HR (318069-02); 8370 and 8371 also listed |
| U3 | Paula 8364 R7 | Paula 8364 R7 (252127-02) |
| U4 | Denise 8362 R8 | Denise 8362 R8 (252126-02); 8373 R2 Denise HR also listed |
| U5 | Gary 5719 | Gary 5719 R2 (318072-01) |
| U6 | Kickstart 1.3 ROM | ROM 256K × 16, Kickstart 1.3 |
| U7, U8 | 8520 CIAs | 8520 R4 CIAs (318029-02) |
| RAM | Sixteen 256K × 1 DRAMs, U16-U31 | Four 256K × 4 DRAMs, U16-U19; U20-U23 not fitted |
| HY1 | Video hybrid | Video hybrid |
The Rev. 5 board takes its chip RAM in sixteen 256K × 1 DRAMs; the Rev. 6A/7 board uses four 256K × 4 parts and leaves four more positions empty.[2] The 8372A Agnus on Rev. 6 boards is the ECS part that can address 1 MB of chip RAM.[3] The jumper pad JP2 that changes the trapdoor memory address for the 1 MB chip RAM conversion is between the Agnus PLCC socket and the CPU socket.[4]
Board revisions
[edit | edit source]Commodore's 1990 service manual documents two A500 main boards: Rev. 5, PCB assembly 312510 with schematic 312511-02, and Rev. 6A/7, assemblies 312510-07 (NTSC) and 312510-08 (PAL) with schematic 312511-03.[2] Community references also list an early Rev. 3 board, which carries its 512 KB of chip RAM as 16 chips, and the Rev. 8A board used in the Amiga 500 Plus.[3] The Big Book of Amiga Hardware describes Rev. 3 as "very buggy".[5]
Memory expansion and clock
[edit | edit source]The trapdoor under the machine takes the A501, Commodore's 512 KB RAM expansion with a real-time clock. The A501 Rev. 6C (assembly 312604-04) carries four 256K × 4 DRAMs at U1-U4, an OKI MSM6242B clock chip at U9 and a rechargeable Varta 3/60DK NiCd battery, 3.6 V 60 mAh, at BT9.[2] The A500 main board itself has no clock or battery.[5] These NiCd cells are prone to leak and damage the board they sit on;[6] see the Amiga 500 Maintenance Guide.
Power supply
[edit | edit source]The A500 runs from an external supply, Commodore part 312503-01, through a five-pin connector: pin 1 +5 V at 4.3 A, pin 3 +12 V at 1.0 A, pin 5 −12 V at 0.1 A, with shield ground on pin 2 and signal ground on pin 4.[2] Ian Stedman's survey of Commodore's supplies lists the 312503-02 at 2.5 A on +5 V (25.7 W) and the 312503-03 at 4.5 A (35.7 W).[7] The supply's circuit is in Sams Computerfacts CSCS26 Amiga 500.
Repair and maintenance
[edit | edit source]- Amiga 500 Maintenance Guide: power supply, A501 battery, cleaning, keyboard and drive.
- Amiga 500 Troubleshooting Guide: Commodore's start-up colours and preliminary checks, chip-level symptoms.
- Amiga 500 Capacitor Replacement Guide: Commodore's electrolytic lists for Rev. 5, Rev. 6A/7 and the A501.
Documentation
[edit | edit source]- Amiga 500 Service Manual (314981-04): Commodore's service manual, October 1990, with troubleshooting, parts lists, board layouts and schematics for Rev. 5, Rev. 6A/7 and the A501.
- Sams Computerfacts CSCS26 Amiga 500: Howard W. Sams service data, 1988, including the power supply schematic.
Gallery
[edit | edit source]-
Commodore's layout drawing for the Rev. 5 main board -
The A501 RAM and clock expansion
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Related pages
[edit | edit source]- Amiga 600
- Amiga 2000
- Commodore 64
- Battery Explosion, Capacitor or Corrosion Damage
- Floppy Drive Repair
References
[edit | edit source]- ↑ 1.0 1.1 1.2 1.3 1.4 Amiga 500—link(accessed 2026-10-01) Release dates, launch price and clock frequencies.
- ↑ 2.00 2.01 2.02 2.03 2.04 2.05 2.06 2.07 2.08 2.09 2.10 2.11 2.12 2.13 2.14 2.15 2.16 Commodore Business Machines, Service Manual A500, PN-314981-04, October 1990, hosted at Amiga 500 Service Manual (314981-04). Specifications, PDF p. 4; start-up sequence, PDF p. 33; major component parts list, PDF p. 49; parts lists for PCB assembly 312510 Rev. 5 (PDF pp. 50-51), Rev. 6A/7 (PDF p. 52) and the A501 Rev. 6C (PDF p. 53); power supply connector, PDF p. 81.
- ↑ 3.0 3.1 Amiga 500—link(accessed 2026-10-01) Board revision summaries: Rev. 3 "512 kB Chip RAM on motherboard as 16 chips"; Rev. 6 "Fat Agnus 8372A (part of the ECS chip set) supports 1 MB Chip RAM"; the A500 Rev. 8 "battery and clock circuit is missing".
- ↑ Amiga 500 mods—link(accessed 2026-10-01)
- ↑ 5.0 5.1 Commodore Amiga 500—link(accessed 2026-10-01) Revision list; "Battery Backed Up Clock: No".
- ↑ A501 coin-cell battery modification, August 2019—link(accessed 2026-10-01) The original cells are "prone to leak green acid, damaging the printed circuit boards".
- ↑ Ian Stedman, Amiga power supply guide—link(accessed 2026-10-01) Table of A500, A600/A1200 and A2000 supply part numbers and ratings.