Atari PCB Revision #s and their Interpretation

[Atarian Computing]

I just went to my shop. Turns out I have 6 Mega ST boards

Funny thing is that the later revision C100167 boards don't have a date on them. Makes it challenging to determine age. It could very well be that early C100167 boards were indeed earliest MST versions but REV 5 could just as well be the very latest version.

I'll update some board pictures in the motherboard section.

Edit: I have twins! Two C103277-___ REV.2.2 boards wk27 1989

[Atarian Computing]

So there are two or three schematics for the Mega ST that I know of,

Schematic labeled C100166 dates from 1987
Service Manual for C100167 with a REV 5 clearly pictured is from 1987
Schematic for C103276 dates from 1988/1989

The more I look into it, I'm getting more convinced that C100167 REV.B is in fact a later revision than C100167 REV.5/4. REV.B is often dated to 1990. REV.5 doesn't have any date code in any board I've looked. The chips on the board however never seem to go past 1988.

One would think that 6-chip TOS wasn't used on later models, yet both REV.B and REV.5 come with 6 sockets. I've seen 1 REV.B with only 2 sockets. Every C103277, C100501, and C103544 only have two TOS sockets. I guess some conclusions can be drawn from that?