Big Book of Amiga Hardware

These are two pre-production boards. The first one is Revision 1 and the second is an earlier revision (although it says 3 on the board). The first one uses ZIP memory while the second uses socketed DILs.
These two are both revision 3 boards. The first one is possibly a pre-production unit, as it is missing the boot ROM and the FPU.
Rev 3 A2620, Front
Rev 3 A2620, Back
Processor: 020@14Mhz
FPU: 68881@14Mhz (PGA). Can be changed to a faster component if a separate crystal is installed
MMU: External 68851 (PGA)
Max Ram: 4MB
Ram Type: ZIP Chips (prototype versions use DRAM Chips with sockets)

An accelerator for the A2000 which plugs into the CPU Fast Slot. This accelerator also has ROMs to support booting the other official Amiga operating system called Commodore Amiga UNIX (Amix). In order to use AmigaOS V2.0+ you need at least version 6.6 of the A2620 ROMs, but preferably V7.0. The right side of the card shows the date and week of manufacture

Jumpers

Jumper On/Up Off/Down
J302 Use 4 Layer (use with German V4.0 A2000 motherboards) Disable 4 Layer
J200 FPU clocked at the same speed as the processor. FPU clocked independently of the processor. (Separate crystal required)
J301 4MB RAM Installed 2MB RAM Installed
J303 Disable Memory Enable Memory
J304 Autoboot Amiga UNIX Autoboot AmigaOS
J500 RAM Timing 80ns RAM Timing 100ns
Page contributors: Dave Haynie, Jan Pedersen, RiWa & Friends, The Man
Updated: 1/2/2005 . Added: 12/22/2004