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

[Kronos]

The A1000 (and A2000A) Agnus is really functional the same as the "Fat Agnus" used in early A500s and A2000Bs. Both come in seperate PAL and NTSC versions and support only 512k chipmem.

The Fat-Agnus also included some additional logic that was build of discreetly on the A1000/2000A.

The Big-Agnus supports either 1 or 2 MB of chipmem is switchable between PAL and NTSC both in HW and SW and allows for bigger blits (but AFAIK noone ever made real use of that).

[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.

[Kronos]

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.

[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

[Zac67]

I've compiled a pinout table for the PLCC Agnus versions and Alice to Wikipedia: MOS_Technology_Agnus a while ago - if that's any help.