MacPlus Board Revisions 820-0174 A-D

I've been able to see that there were at least four revisions of the MacPlus board (820-0174 A-D). What I am unable to find is any definitive information on what (if anything) changed between these revisions.

Anyone able to shed any light on this?
 
The only thing i can think of are Roms, they are several available, so maybe the revisions are following Roms.

Probably also some changes in the Logic Board design, but should be pretty light.
 
The only thing i can think of are Roms
I was thinking that too. I have a 128KB that was old school kit upgraded to the Plus. That has the A revision in it. I just built a CatMac MacPlus and that has a C revision. And for good mid life crisis measure, I just found and ordered a D revision.

For my existing A and C revisions, I did pull the ROM ICs and replace with Rominators. But now I will go dig up the original ICs to see how they are labeled. May even throw them back in and do a DM in MacsBug to see their ROM checksums.

Digging into this mostly for knowledge accumulation. And secondly I am planning on putting the revision D into the CatMac case; and I want to get an '030 accelerator for it. So then it will be the ultimate Plus Plus.
 
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