In 1987 Commodore released its
first highly expandable machine, the A2000. Early models are based around the
A1000 design but most models are built around the A500 chip set. The A2000HD
shipped with an A209x SCSI controller and a SCSI hard disk drive installed. The
A2500 has a processor card added to the A2000HD configuration. The A1500 shipped
with two floppy drives but no hard disk drive.
The A2500UX shipped with AT&T Unix System V Release 4 operating system instead of AmigaOS, a three button mouse, and usually with a tape streamer and Ethernet card.
68000 @ 7-28 MHz
68020 @ 14-25 MHz
68030 @ 16-50 MHz
68040 @ 25-40 MHz
68060 @ 50 MHz
The A1500 and most A2000s have a socketed 68000 @ 7.14 MHz processor on their motherboard and they shipped with an empty processor slot. Early A2000s and the A2500 use a processor card. The A2500/020 shipped with an A2620 processor card featuring a 68020 and 68881 @ 14 MHz, and the A2500/030 with an A2630 featuring a 68030 and 68882 @ 25 MHz.
up to 2 MB Chip RAM
up to 128 MB Fast RAM on processor cards
up to 8 MB Fast RAM on Zorro II expansion cards
Most A2000 models have 1 MB RAM
soldered to their motherboard. Early models, the 3.x series, have 512 kB Chip
RAM on their motherboard and 512 kB Fast RAM on their processor card. The 4.x
series have both 512 kB Chip and Fast RAM soldered to their motherboard, whilst
the 6.x series have their RAM set up as 1 MB Chip RAM.
24 bit Fast RAM can be added using Zorro II expansion cards up to 8 MB, and 32 bit Fast RAM using processor cards featuring a 68020 or better.
Agnus / Fat Agnus - OCS / ECS
Denise / Super Denise - OCS / ECS graphics coprocessor
Paula - audio and I/O controller
Gary - system address decoder
Buster - DMA arbitrary controller
The A2000's OCS or ECS chip set offers the same screen modes as the A500 and A500 Plus:
|50 Hz, 15.75 kHz
50 Hz, 15.75 kHz
60 Hz, 15.75 kHz
60 Hz, 15.75 kHz
400×300 - 800×600
|50 Hz, 31.5 kHz
72 Hz, 24 kHz
1× processor card slot (CPU
5× Zorro II slots
1× video slot
2× inactive AT ISA slots
2× inactive XT ISA slots
The Zorro, ISA and video slots
are all placed on the motherboard. Two AT ISA slots are in line with a Zorro II
slot, while the XT and video slots are not.
In early A2000s the video slot just use the signals of the external 23 pin video connector, others are extended with the remaining digital video signals and some parallel port lines.
The four ISA slots have their power and ground pins activated only. In order to access the slots by the A2000 a BridgeBoard has to be installed. With an installed BridgeBoard, two or three ISA compatible cards can be used depending on the BridgeBoard's position - if it is installed in slot 3 two ISA and four Zorro cards can be used, if it is in slot 4 three ISA and three Zorro cards are possible. Inactive ISA slots can be used for non intelligent cards like TBCs or fan cards. The two XT ISA slots can be upgraded to AT slots by simply soldering the 16 bit extension slots.
Early A2000s implement an internal version of the A1000 external edge connector as processor card slot. All other revisions use a 86 pin processor card slot with a coprocessor interface which allows processor cards to be added without the need to remove the 68000.
2× 3.5" front bays
1× 5.25" front bay
In the A2000 one, in the A1500 both of the 3.5" bays are occupied with 880 kB double density floppy disk drives.
1× serial DB25 male, RS232
1× internal serial 26 pin header
1× parallel DB25 female, Centronics
1× video DB23 male, analog RGB
1× composite, black & white
2× mouse/game DB9 male
2× stereo audio RCA jack
1× keyboard 5 pin DIN female
1× external floppy DB23 female
1× internal floppy 34 pin header
The floppy drive controller
supports up to four devices - two attached to the internal floppy header and two
connected to the external floppy port. Both double and high density disk drives
The internal serial header has the same address as the external one. It is intended to be used with internal MIDI interfaces.
It is based on the integration of the A1000 motherboard design and an example Zorro II backplane. It uses the thin Agnus which handles only 512 kB RAM. The video slot is just an internal version of the external video port and the processor card slot is just an internal version of the A1000 external edge connector. The A2000-A has many reliability problems.
It is basically a cost reduced version based around the A500 chip set. Most of the control logic for the expansion bus is integrated into the Buster. The video slot is extended with more signals and the CPU slot has a coprocessor interface. The 68000 and 1 MB of RAM is placed on the motherboard.
220 W power output
2× standard 4 pin power connectors
2× mini 4 pin floppy drive power connectors