Amiga 2000 Green Screen

[Pat the Cat]

Suggest you do a search here for "green screen".

You would not get it if CPU was damaged - at least ROM code to do the tests is being run.

However, the tests are pretty quick and slapdash. A bus error preventing chip RAM from being read may also cause a green screen.

Sometimes is a faulty RAM chip, sometimes faulty Gary or (on an A2000) Buster or Ramsey or even just a short on the slots - old bit of solder, that kind of thing. I've found usually is a short or a corroded socket pin, not a real problem with a chip as such.

Also try swapping the 8520s, if one is bad and causing bus error, might resolve the boot and show the fault to be in an 8520 rather than a RAM chip.

If you do end up swapping out DRAMs (not applicable this case), do fit sockets if not fitted already. Also check Rev 6 mods are all in place and haven't been undone.

EDIT: Pic shows very tidy board. Is cap to left of CPU shorting on pin? Probably not, just optical illusion.

[Pat the Cat]

IIRC original A2000 shipped with 512K "pseudo fast" and 512K chip... so for some reason thinks it isn't quite a Rev 6 motherboard.

Gary would be my prime suspect, but like I said, typically isn't a bad chip, is a short somewhere. Agnus too but you seem to have covered that base already.

I had no idea about DiagROM either. I guess I am used to diagnosing by swapping chips out...

Thank you too Acii, and to Mr Hertell for doing the work with DiagROM.

Also, check links to select 1MB Chip Ram / 512K+512K split.

Memory map here, looks more like first 256K isn't accessable for some reason... maybe I am reading this totally wrong.

http://amigadev.elowar.com/read/ADCD_2.1/Hardware_Manual_guide/node00D3.html

ALso J500 may be set wrong, does not just disable clock, also disables some chip RAM.

http://www.titan.co.nz/amigaak/AA060161.htm