Reply 40 of 43, by TubeTimeUS
FWIW, the MCGA chips have been decapped and imaged:
https://siliconpr0n.org/map/ibm/72x8300/mz_mit20x/ - 72X8300
https://siliconpr0n.org/map/ibm/72x8205/mz_mit20x/ - 72X8205 (partial: top metal layers accidentally got removed)
https://siliconpr0n.org/map/inmos/imsg171a/mz_mit20x/ - IMSG171A RAMDAC