version of the Amiga 2000
computer. The Amiga 2500 was simply an Amiga 2000 computer with the addition of a hard drive
and a CPU accelerator
board. The system came in two versions: the original A2500/20 and the later A2500/30. The numbers simply refered to the model of the accelerator board included, either the A2620 (a Motorola 68020
based board) or A2630 (a Motorola 68030
based board). The A2500/20 was originally released in 1989, succeeded by the A2500/30 in late 1990.
While the A2500/30 wasn't quite as fast as the Amiga 3000, it did have the advantage of being far more compatible with older software, due to the legacy Motorola 68000 CPU on the unmodified A2000 motherboard. Many programs written for the original Amiga systems weren't compatible with the 68030, basically due to the fact that some programmers disregarded the programming guidelines set by Commodore. Having the 68000 available made it possible to run this non-compliant code. The CPU selection was made at boot-time by holding down both mouse buttons and then selecting from a graphical menu. An interesting fact is that the original A2620/A2630 ROMs contained an option to boot into Amiga's special version of UNIX, if it was installed.
As for the hard drive, the standard Amiga 2000 didn't come with a hard drive unless you purchased the Amiga 2000HD version. The typical hard drive sizes were 50MB or 100MB, and quite often were Quantum LPS SCSI drives.
One interesting technical note about A2500 systems was that the accelerator boards contained additional memory for the user. This additional memory, unlike the memory on the motherboard or other Zorro II cards, was 32-bit instead of 16-bit. Since the Amiga had distinctions between chip RAM (slow memory that the Amiga's coprocessors could use) and fast RAM (which the coprocessors could not use), this added a third type of memory, 32-bit fast ram. When optimizing an A2500 for fastest operation, the goal was to get the critical parts of the operating system in to this 32-bit fast RAM for ultimate performance.