What A2000 MoBo can have 1MB chip RAM ?

[Lokki]

Zac67 wrote:
As melange stated, you need an ECS Agnus (numbers vary) and to reset a jumper. AFAIK 8375 will work.

8375 isn't pin compatible so don't just plug one in and try it!

[Lokki]

I can't spot my schematic with 8372B just at the minute but I'm pretty sure they're not a straightforward swap either, especially not if the A2000 is running OCS...

[Lokki]

I read those posts a while before I started posting myself, when I was still collecting schematic diagrams.

A more useful source of information for those wanting to do some serious hardware hacking would be a pinout table.

[Lokki]

melange wrote:
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 just found my other schematics and it looks like putting an 8372B into an A500 rev6 or higher is just a matter of cutting and jumping points at JP5. A20 replaces the XCLK signal from the Agnus so you're just jumping pin 35 to A20 and then giving XCLK an alternate source. I'd imagine the higher revision A2000s would have a similar point to JP5.
My bad!

[Lokki]

This is taken from one of the miscellaneous docs I've been reading, not sure where it's from or who originally wrote it:


Find Jumper J101 located on the lower right side of the power connector CN400, and consists of 3 posts - 2 of the posts are shorted together using a shorting block. Remove the shorting block and move it to the left, towards the power connector. For further info, see Page 13 of the A2000 system schematics - this jumper will enable address line 19 from the 68000 which controls the 1 meg address range.

Locate and cut Jumper pad J500 (to the lower left of the 8520 at U301). This is a 2-pad jumper with a trace connecting the two pads. See Page 9 of the A2000 system schematics - cutting this trace keeps the _EXRAM signal from being tied to ground.

To enable PAL rather than NTSC - locate and cut J102, NOT J201 as suggested in some docs. This is the equivalent of bending pin 41 of Agnes in the A500 mod.

[Lokki]

That's what the agnus substitution doc said... I'm not saying it's gospel, it's been too long since I saw inside an A2000. That and I can't find my A2000 schematics, I seem to have misplaced them.
It sounds about right though.

[Lokki]

No worries mate, good to have confirmation of it too!  :-)