Amiga 2000

Commodore Amiga 2000

Type	Personal computer
Release date	March 1987 (1987-03)
Introductory price	USD 1495 (1987) USD 3,100 (2016 equivalent)[1]
Discontinued	1991
Operating system	Amiga OS 1.2/1.3 or 2.0
CPU	Motorola 68000 @ 7.16 MHz (NTSC) 7.09 MHz (PAL)
Memory	1 MB (9 MB maximum)
Predecessor	Amiga 1000
Successor	Amiga 3000

The Amiga 2000, or A2000, is a personal computer released by Commodore in March 1987.^[2][3][4] It was introduced as a "big box" expandable variant of the Amiga 1000 but quickly redesigned to share most of its electronic components with the contemporary Amiga 500 for cost reduction. Expansion capabilities include two 3.5" drive bays (one of which was used by the included floppy drive) and one 5.25" bay that could be used by a 5.25" floppy drive (for IBM PC compatibility), a hard drive, or CD-ROM once they became available.

The Amiga 2000 is the first Amiga model to have allowed expansion cards to be added internally. SCSI host adapters, memory cards, CPU cards, network cards, graphics cards, serial port cards, and PC compatibility cards were available, and multiple expansions could be used simultaneously without requiring an additional expansion cage like the Amiga 1000. The Amiga 2000 not only includes five Zorro II card slots, the motherboard also has four PC ISA slots, two of which are inline with Zorro II slots for use with the A2088 bridgeboard, which adds IBM PC XT compatibility to the A2000.

The Amiga 2000 was the most versatile and expandable Amiga computer until the Amiga 3000T was introduced four years later.

Features

Inside of the Amiga 2000 (hardware revision 6.2). The third and fourth slots from the left are bridge slots, with Zorro II connectors inline with ISA connectors.

Aimed at the high-end market, the original Europe-only model adds a Zorro II backplane, implemented in programmable logic, to the custom Amiga chipset used in the Amiga 1000. Later improved models have redesigned hardware using the more highly integrated A500 chipset, with the addition of a gate-array called "Buster", which integrates the Zorro subsystem.^[5] This also enables hand-off of the system control to a coprocessor slot device, and implements the full video slot for add-on video devices.

Like the earlier model, the Amiga 1000, and most IBM PC compatibles of the era, but unlike the Amiga 500, the A2000 comes in a desktop case with a separate keyboard. The case is taller than the A1000 to accommodate expansion cards, two 3.5" and one 5.25" drive bays. The A2000's case lacks the "keyboard garage" of the Amiga 1000 but has space for five Zorro II expansion slots, two 16-bit and two 8-bit ISA slots, a CPU upgrade slot and a video slot. Unlike the A1000, the A2000's motherboard includes a battery-backed real-time clock.^[6]

The Amiga 2000 offers graphics capabilities exceeded among its contemporaries only by the Macintosh II, which sold for about twice the price of a comparably-outfitted Amiga 2000 additionally equipped with the IBM PC Compatible bridgeboard and 5.25" floppy disk drive (which was important for real-world interoperability at this time).^[7] Also like the A1000, the A2000 was sold only by specialty computer dealers. It was originally announced at a price of 1495 USD^[1]

The A2000 was largely succeeded by the Amiga 3000 in 1990. The 3000 features fewer options for internal expansion than the 2000 models, so Commodore supplemented the Amiga 3000 with the Amiga 3000T in 1991.

Variants

The Amiga 2000 was always designed with an open architecture. Commodore's engineers believed that the company would probably be unsuccessful in matching the rate of system obsolesce and replacement then common in the PC industry, with new models every year or so. Commodore's approach was to build a single system architecture that could span different models. Commodore was so successful at this that Info magazine judged that the A2000 would not become obsolete "until well after the turn of the century"^[8] at the earliest.

The final design was the result of an internal battle within Commodore, which pitted the USA division, who wanted to build a system more like the Amiga 3000 (and 1000), against the German division, which was fresh off the successful introduction of the first Commodore PC compatible systems and planned to include this capability in the Amiga 2000 from the start.^[9] The bottom-line practicality of the German design won out, and the final A2000 shipped with not only Zorro II slots, but a compliment of PC standard (for the day) ISA slots.

This architecture was subject to major revisions. The "B2000-CR" motherboard was the most common, showing up as the first major revision. It was designed by Dave Haynie and Terry Fisher (whose names are printed on the board) and, while an A2000 variant, was a redesign of the Amiga 1000 motherboard incorporating some Amiga 500 technological advances to achieve the "CR": Cost Reduction.

The original Amiga 2000 shipped with just a single floppy drive for storage. This was followed up fairly early by the Amiga 2000/HD, which bundled an Amiga 2090 hard drive controller and a SCSI-based hard drive. In 1988, Commodore shipped the Amiga 2500/20, which added the Amiga 2620 CPU card to the CPU slot, a 14.3 MHz 68020, a 68881 FPU, and a 68851 MMU to the A2000, along with 2 MB of 32-bit-wide memory. The A2000's original 68000 CPU remained installed on the motherboard of these machines, but was not used. In 1989, this model was replaced by the Amiga 2500/30, which added an Amiga 2630 CPU card: 25 MHz 68030 and the 68882 FPU with up to 4 MB of 32-bit memory. The A2630 card could also take a memory expansion daughter card, capable of supporting up to 64 MB of additional memory. Commodore built an in-house prototype of this, but never released one.

Amiga 1500

In 1990, Commodore UK sold a variant of the A2000, the A1500, for £999. The model designation was not officially sanctioned by Commodore International. The A1500 shipped with dual floppy drives, and 1 MB of ChipRAM as standard. Initial units came with Kickstart 1.3 (and thus AmigaOS 1.3), though the Original Chipset onboard includes a later Agnus revision allowing the 1MB of ChipRAM. Early machines were bundled with a Commodore 1084SD1 monitor. Later machines came with the ECS chipset and AmigaOS 2.04. The second floppy drive replaces the hard disk drive. The A1500 has no hard disk drive as standard.

A1500s are easily convertible into A2000/HDs by addition of a hard disk controller (and associated drive), and then simply peeling off the A1500 label revealing the A2000 label beneath.

The reason for the UK-only release may have been the existence of a desktop upgrade kit for the Amiga 500 made by Checkmate Digital and also called A1500,^[10] and Commodore's trying to keep the name for themselves.

Amiga 2500

The Amiga 2500, also known as the A2500, is not a distinct model, but simply a marketing name for an Amiga 2000 bundled with a Motorola 68020 or 68030-based accelerator card.^[11] The accelerator cards used by the A2500 (the A2620 and A2630) were also available separately as upgrades for the A2000. 68030 versions were referred to as A2500/30.^[12]

Because the A2500 has a Motorola 68000 on the motherboard that goes unused, the design is not very cost-effective. A project to replace it with a 68020 on-board began, intending to be a Zorro-II-based 68020 machine, but the project eventually became the Amiga 3000 when Dave Haynie sought to include his new Zorro-III bus.

The A2500 remained in production after the release of the A3000, primarily because the original Video Toaster will not fit in an unmodified A3000 case. Until the release of the Video Toaster 4000, the A2500 was the fastest computer available for use with the Toaster.

A variant of the A2500 called the A2500UX was also available which was supplied with Commodore Amiga UNIX and Tape Drive ^[13]

Technical information

The majority of A2000 systems shipped with Commodore's Original Chip Set and 1 MB of RAM (512 KB of "chip" RAM and 512 KB additional RAM) and either AmigaOS 1.2 or 1.3. Later revisions shipped with the improved Enhanced Chip Set, 1 MB "chip" RAM and AmigaOS 2.0.^[14]

The A2000 shipped with a Motorola 68000 CPU, running at 7.16 MHz (NTSC) or 7.09 MHz (PAL). The CPU can be upgraded to a 68010 by direct replacement. Official and third-party expansion boards, which fit in the CPU expansion slot, feature 68020, 68030, 68040 or 68060 microprocessors. Such upgrades may also accommodate additional RAM, FPUs, MMUs and even SCSI controllers.

Memory capacity varies according to the hardware revision. Certain revisions of the A2000 can be upgraded to accommodate 1 MB of chip RAM by installing an 8372A Agnus chip. Likewise, 2 MB can be accommodated by fitting an 8372B Agnus chip and adding extra memory. There is a practical limit of 8 MB of additional RAM without the use of a CPU expansion card, due to the 68000's 24-bit address bus.

The A2000 brought a new capability to the Amiga line, the Zorro II bus. This expansion bus allows installation of compatible hardware through the AutoConfig standard, such as, graphic, sound, and network cards and Parallel ATA, SCSI and USB controllers.

The ISA slots can be activated by use of a bridgeboard, which connects the Zorro II and ISA buses. Such bridgeboards typically feature on-board IBM PC Compatible hardware, including Intel 80286, 80386 or 80486 microprocessors allowing emulation of an entire IBM-PC system in hardware. The remaining ISA slots allow can then be used with industry standard hardware of the era, such as, network cards, graphics cards and hard drive controllers. In some A2000 models, the two 8-bit ISA slots can also be upgraded to 16-bit by fitting extension edge connectors.

The video slot presents clocks, all 12-bits of digital video, Genlock signals, and some control lines for use to add-on cards. This allows use of dedicated genlocks, display deinterlacers, and video-switching and effects systems such as NewTek's Video Toaster.

Specifications

Notes

1. ^{^} Model A (revision 3.0-4.0), 1986
2. ^{^} Model B (revision 4.1-5.0), 1986
3. ^{^} Model C (revision 6.0-6.5), 1991

See also

• Amiga models and variants

References

External links

• amigahistory.co.uk/a2000 – History of the Amiga 2000
• Info magazine preview of the A2000 and A500
• Amiga 2000 teardown

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