RetroWiki

This is the workhorse of the series. While the A1000 introduced the world to Amiga and the A500 was the gamer edition the Amiga 2000 was expandable, high performance, high price, and had the chops for the new field of video production.

Chips

• Agnus
  • the name Agnus is derived from 'Address GeNerator UnitS' since it houses all address registers and controls memory access of the custom chips
  • manages all RAM intereactions
  • blitter - a sub component is responsible for
  • copper - a sub component is a co-processor for
• Buster
  • is the DMA arbitrary controller
• Denise
  • the name Denise is a contrived contraction of Display ENabler
• Gary
  • system address decoder
• Paula
  • the name Paula is contrived contraction of Ports, Audio, UART and Logic, and coincidentally the chip designer's girlfriend

Recap The best thing you can do for your 30+ yr old retro computer is to recap it. The electrolytic capacitors just loose their juice (actual fluid) over time. Keep in mind, it doesn't matter if the voltage rating on the capacitor is higher than the original rating.

The Rev 4 motherboard needs 29 capacitors

• (3) Radial 4,7 uF
• (7) Radial 22 µF
• (4) Radial 47 µF
• (5) Radial 47 µF (other diameter)
• (1) Radial 100 µF
• (5) Radial 220 µF
• (4) Radial 470 µF

The Rev 6 motherboard needs 32 capacitors

• (3) Radial 4,7 uF
• (7) Radial 22 µF
• (13) Radial 47 µF
• (1) Radial 220 µF
• (4) Axial 220 µF
• (4) Radial 470 µF

The motherboard is plenty safe to do yourself. Keep in mind the capacitors by the Zorro slots can be either radial (can sitting on top) or axial (lying on its side like a log).

Check out this link for some power supply recapping information. Remember, those big caps have enough stored electricity to give a serious shock or kill you. Follow proper safety procedures for discharging them before you go poking fingers or metal objects in there. See — http://blog.worldofjani.com/?p=6375

• Blank screen, things to check
  • check Agnus is seated correctly, re-seat if necessary
  • swap KS ROM
  • swap in CIA chips, swap one at a time
  • no instant red means that the KS ROM is being read OK and the checksum has passed
• Yellow indicates
  • memory issue so remove any memory expansions if present
  • yellow/green can sometimes be cured by re-seating Agnus
• Gray screen
  • most likely chip RAM
• Red screen

CIA 8520 common failure symptoms are:

• dead or flakey floppy drive. DF0:???, icons for nonexistent drives showing up, motor always on, head step problems, etc.
• dead or flakey parallel port
• no mouse/joystick fire buttons. (left mouse=fire)
• TOD clock not advancing, or only advances a few seconds and resets.
• CLI works okay, but double-clicking on WB icons hangs WB.
• keyboard problems about 30% of the time. Usually it's a bad 6570 micro in the keyboard.
• data errors on the floppy or serial ports are not necessarily 8520 failures. The data from these devices goes to Paula, and in owning and tinkering with Amigas since 1986, I've never seen a bad Paula.
• joystick or mouse directional failure is NOT 8520 related. This is a common misconception. Probably the fuse that looks like a resistor
• CIA at U8 is responsible for the floppy select, motor enable and head step functions
• CIA at U7 is for disk change, track 0 selection, the ready signal and write protect
• C64's 6526 and Amiga 8250 are basically compatible and swappable - one difference is 4 byte BCD time of day counter being replaced with (much more useful) 3 byte binary counter

• convert A2000 OCS to ECS
  • do it? nah, a fun project but little reward
  • replace Agnus with a FAT(1MB) or FATTER(2MB) version
    • an Agnus 8372B (found in A3000s)
    • an Agnus 8375 + adapter (there are a few pinouts different from 8372)
    • for gaming you only need a 1MB Agnus, there are not many games built for ECS
    • for video production you need a 2MB Agnus
  • Super-Denise (ECS) 8373 R4
    • a drop in replacement
• 68010
  • do it? yup, it's easy, non-destructive, and you get a mini boost
  • the 68010 has extra instructions programmed into the CPU
  • it does some fancier calculations, for instance compression
  • just pull the 68000 and install the 68010
  • testing will show a 5-10% improvement in performance, it so minimal that you may not see the change
  • there are rumors that some programs which require a 68020 will run on a 68010, this goes back to the extra instructions in the 68010 CPU
  • there may be problems with some games which can be solved by a software patch (decigel), the patch has to be loaded first
• NTSC/PAL switch
  • do it? yup, it's easy, non-destructive, and allows some bitchin PAL demos
  • there is a solder blob (some may have a jumper) on J102, which is grounded
  • desolder that, and solder two wires to an on/off switch
  • you can drilled a hole in one of the slot covers, install a small switch, then it's a reach-around to enable the NTSC/PAL mode
  • if you have a Gotek drive in place, install the switch there, I like a bunch of switches and blinky lights on things