Agnus, Fat Agnus, Fatter Agnus pinouts/schematics?

[Digiman]

I was googling for some technical info for pinouts on the original Agnus (A1000 version) and Fat Agnus (A500/2000 512kb chip ram model) and Fatter Agnus (8372 with 1mb max chip ram)

So...apart from packaging what is different between these three versions of Agnus? I know 8375 Obese Agnus has different pinouts and is not compatible already.

TIA

[Digiman]

As far as I can tell there were 4 versions of Agnus.

DIP package for A1000 only which has the same size/packaging as Paula and Denise.

Fat Agnus which is the big square design for A500/2000/1500 machines but identical in features.

Fatter Agnus eg 8372A which was the first 1mb chip ram capable but before A500+ ECS machines.

And Rev 6 A2000/A500+ which had the 8375 Agnus which can go up to 2mb chip. This was also different in the A600/3000 version of Obese Agnus which is not a direct replacement.

What I am trying to find out is if there is only a physical difference between the A1000 slim DIP Agnus of A1000 and the square Fat/Fatter Agnus of the A500/A2000. ie was there an actual reason for having Fat Agnus because functionally my early A2000 with said version is no different to my A1000 with slim Agnus.

edit: This is not for making 1mb chip ram for my A1000, that's not really possible I don't think as the motherboard is 256kb and 256kb front expansion max, it's more for rarity for a machine that fails.

[Digiman]

If I remember correctly the stuff that went into Fat-Agnus was the logic for generating the RAM-Refresh. Piggybacking a Fat-Agnus onto an A1000 (or A2000A) would equire to disable/bypass this logic either in the Fat-Agnus or on the motherboard.

From  a SW point of view there is no way of telling a slimm-Agnus from a (non Big) Fat-Agnus.

Ahh OK this is beyond the simple 'adaptor design' to fit a different chip package then. Thanks for the info