The AMIGA 3000 is regarded by some Amiga fans as the best model ever made, but they generally forget about the AMIGA 3000T and AMIGA 4000T which actually offer a lot more. The AMIGA 3000 unlike most Amiga models, supports both ROM based Kickstarts and disk based Kickstarts, although not simultaneously. Kickstart V1.4 is actually a special version of Kickstart which loads the real Kickstart from a file called DEVS:Kickstart. Kickstart V2.04 was available as a ROM, or as a disk based version for use with AMIGA 3000's which had Kickstart V1.4. AMIGA 3000's fitted with Kickstart V1.4 cannot use 68040 or 68060 processors, regardless of what version of Kickstart is eventually booted, because it relies heavily on the integrated MMU in the 030 which varies to some degree from the MMU in 680040 and 680060 processors. The AMIGA 3000 also contains a built in scandoubler and flicker fixer so that standard PC type SVGA monitors can be connected and display the native (PAL/NTSC) screen modes. It was available as a separate card for other Amigas called the A2320. The scandoubler can be disabled if necessary by a switch on the back of the machine. There is also a variable switch to finetune the scandoubler. The AMIGA 3000 has a SCSI-II controller (WDC33C93) on the motherboard which is much faster than the standard IDE Controller that was supplied with the AMIGA 4000 and other models. However some motherboard revisions have SCSI termination directly on the motherboard and others don't. You may find you need at least one SCSI device attached in order to boot, even from floppy disk. The AMIGA 3000 is one of the few models of Amigas which actually has some NVRAM, primarily for storing the configuration settings of the SCSI controller, such as Controller ID, SCSI bus timeout, Synchronous mode and LUNs.

There are RAM sockets on the motherboard for expanding CHIP RAM up to 2MB, providing your Agnus chip supports it. These are in the form of DIP sockets. The motherboard also contains 32 ZIP CHIP sockets and 20 DIP sockets for adding additional memory. If the DIP sockets are used then only a maximum of 4MB of Fast RAM can be added. If ZIP memory is used then 16MB of Fast RAM can be added. The ZIP and DIP sockets cannot be used simultaneously. If you intend to use Zorro III cards which make use of Zorro III DMA then you need to upgrade Buster to Rev 11. The Zorro III and ISA expansion slots are on a daughterboard (riser card) which is connected to the motherboard and rises vertically from it.

SCSI Problems

The AMIGA 3000 may suffer SCSI related problems when several SCSI devices are attached to the bus. The most common are random SCSI bus lockups, especially with CD-ROMs and tape driver and random checksum errors when copying large files between devices. These problems can, in most cases (providing termination and jumpers are correct) be attributed to the WD33C93A SCSI controller chip in the AMIGA 3000. Most, if not all, AMIGA 3000s shipped with the WD33C93A-PL 00-04 chip revision. This chip had known bugs when multiple devices were present on the SCSI bus. The WD33C93A-PL 00-08 chip revision addresses and fixes the above problems.

WD33C93A-PL 00-08 9131 F (Latest Revision)
WD33C93A-PL 00-04 9201 D (default release)

INT2 Modifications

Certain accelerators, primarily those with onboard SCSI may require the INT2 modification to function fully. The AMIGA 3000's CPU Fast Slot does not contain the INT2 signal as found on the AMIGA 3000T, AMIGA 4000 and AMIGA 4000T. An INT2 modification guide can be found here.

Motherboard Layout

1. RCA Stereo Jacks
2. VDE selector switch
3. Video finetune adjustment
4. VGA connector
5. Amiga Video connector
6. SCSI & Parallel port
7. External Floppy
8. Serial port
9. Amber gate array
10. System expansion bus
11. Super DMAC gate array DMA controller for SCSI
12. System ROM
13. Paula Audio I/O
14. Denise Enhanced 1280 hires
15. Fat Agnus
16. Fat Gary gate array system address decoding
17. Fast RAM
18. Chip RAM
19. Fat Buster gate array DMA Arbitur for motherboard
20. MC68030 microprocessor 16/25 Mhz
21. MC68881/82 Math coprocessor
22. Ramsey gate array Dynamic-static RAM controller
23. Fast RAM (DIP)
24. CPU Fast Slot
25. Mouse/Joystick
26. Mouse/Joystick
27. Keyboard
28. Internal SCSI and Floppy Connectors
29. System power 135 Watt power supply

Jumpers

Notes:
J150, J151: ROM Timing.
The ROM timing circuit provides four different speed settings to match the output enable and access timing of the system ROMs. To set the jumpers, determine the output enable time and access times for the ROMs you wish to use. The ROM must have lower values than the setting you select. System standard ROMs have T(oe) = 110ns and T(acc) = 250ns.

Source : http://www.amiga-hardware.com/