What A2000 MoBo can have 1MB chip RAM ?

[melange]

You have the German 4 Layer Mobo I think.  There is probably a Jumper that you can set to change from 512K to 1MB Chip.  You must have an 8372A Agnus in there at least.  You could use the 8372B (I think) but you would still only be able to address 1MB of chip.
You would need to find a Mega-CHIP or TOP-CHIP 2MB Chip upgrade, (Just sits in the agnus socket).  Those are hard to come by.  I just paid an arm and a leg for one.  You should certainly get the 1MB Chip going though.  It's odd because both my A2000's were 1MB chip as standard.  Must be the German Mobo.  There are documents on the net that will explain the Jumpers for you.  Just do some googling.

If you have an 8371 Agnus, then replace it with an 8372A at least, or you cannot go to 1MB Chip.

Oh and if your going to remove the Agnus, make sure you get a PLCC chip puller, or you WILL break the socket for sure.
Good luck  :-)

[melange]

I wasn't sure of that, but what I do know is that I have an A500 with a 2MB Chip board called an AX-RAM 4.  It has an 8372B Agnus and an acompanying Gary daughter Board with programmed chips (PAL) to make it all work.

  I also have a TOP CHIP 2MB Chip expansion in one of my A2000's, it also has an 8372B and sits on a mini pcb board, that plugs into the Agnus socket (there is extra logic all around that pcb in the form of smd chips). The top chip also has a Gary daughterboard also containing extra logic.  It dosen't seem to be that straight forward.  Think there is probably a bit of work in that hack whichever way you go about it.

[melange]

sorry rkauer

8372A is PAL or NTSC (Depends on your machines default configuration, can be easily set to either with a wire/jumper) ECS 1 meg Agnus!

8372B is PAL or NTSC (Depends on your machines default configuration can be easily set to either with a wire/jumper) ECS 2 meg Agnus!

I know this because I have used both chips, and had a hard hack using a switch between the PAL/NTSC pin on the Agnus and Earth.

This would allow me to change to NTSC for some games and get a smoother 60hz play.  I preferred to powerdown when switching over, but I think it was considered safe to do it on the fly.

[melange]

Yep, that sounds about right.  In the A500 Rev 5, the same hack can be applied, but tracks need to be cut and wire links soldered in.
My first A500 was Rev5 which I had my 4MB AX-RAM card in.  It had tracks cut and links soldered in.

When I got a Rev6 Board, I only had to cut jumping points and join jumping points which was easy.