The Commodore Amiga 2000 is the successor of the Amiga 1000. As the Amiga 500 was the "low-end" model of the new products, the 2000 was considered the "high-end" model in 1985.
Like the original Amiga, it uses the same memory configuration with chip RAM (512 KB which can be accessed by the custom chips) and fast RAM (the rest of memory which can be accessed only by the CPU).
There are three drive bays : two 3.5" front bays and one 5.25" front bay. A 5.25" floppy drive or a half-height hard drive could be mounted into this last bay.
A Commodore 8088-CPU bridgeboard (a PC-on-a-card) was available. When operating, 128k RAM is used as a "bridge" between the PC bus and the Amiga Bus. Two programs (called ARead and AWrite) make the data exchange between PC and Amiga possible. The ISA slots can be used only with the "bridge" card and are unused in "Amiga mode".
There are in fact 3 models and many variations of the A2000 :
The Amiga 2000A, the "original A2000" was designed in Germany and was based on a German Amiga 1000 motherboard. The system was based upon an interesting design but was restricted in many ways (the thin Agnus could only use 512 Kb RAM). The machine had a number of reliability problems representing a refinement of 1985 technology rather than an step forward.
The Amiga 2000B is a kind of mix between the redesigned German 2000A and a cost-reduced version of the A500. It is generally referred in the UK as the B2000.
The Amiga 2000C is the final version of the A2000. It is based upon the improved ECS Chipset, but otherwise it is identical to the 2000B. It is known as the Amiga 2000+ in the US and was shipped with the new improved Kickstart 2.04.
The model with a built-in disk controller and a hard disk was called the Amiga 2000HD, it was shipped with an A209x SCSI controller and a SCSI hard disk drive installed.
The A2500 systems were based upon the final revisions of the A2000-B motherboard design before the A3000 was released.
The A1500 was a UK-specific machine derived from the A2000, retailing at £999 (UKP) during 1990. Apart from shipping with two floppy drives, 1Mb memory and a new nameplate there is hardly any difference between the A1500 and the A2000.