Genesis:32X Model Differences

Some page content & researching taken from io55.net's Genesis Add-Ons page with permission, in collaboration.

Note that both 32X revisions have compatibility problems on certain model 1 consoles, which can be corrected. Both revisions also have problems with the VA2.3 and VA4 model 2 consoles, for which there is currently no documented fix aside from loading games from a flash cart instead of original cartridges.

VA0/MK-84000 (1994-1995)

These 32Xs have some problems with the VA0 model 2. If nothing is plugged into the side expansion slot (typically used by the Sega CD), many 32X games will refuse to work or lock up within minutes. This can largely be fixed on the VA0 model 2 by connecting a Sega CD or using the Extension Unit which came bundled with the 32X. The Extension Unit acts as a terminator on the expansion port and contains pull-down resistors on the data bits (pins A4 through A11 and A13 through A20). This will not fix issues with the 32X on the VA2.3 and VA4 model 2s.

VA1/MK-84000A (1995-1996)

Some of the model 2 compatibility issues were fixed with this revision as it added pull-down resistors on the data bits, eliminating the need for the Extension Unit.

References

https://gametrog.com/sega-32x-information-specs/ (incorrect on version differences, slightly)

https://www.reddit.com/r/SEGA32X/comments/24snek/i_recently_found_one_of_the_mysterious_32x/

https://www.reddit.com/r/SEGA32X/comments/e6qbcj/knuckles_chaotix_issues_with_sega_genesis_model_2/

https://www.reddit.com/r/SEGA32X/comments/9ryglb/question_about_the_32x/

https://www.reddit.com/r/SEGA32X/comments/4m9ol7/sega_32x_model_revision_region_bypass/

https://www.sega-16.com/forum/showthread.php?23611-How-can-you-tell-the-difference-between-the-32x-revisions-and-what-makes-the-2-units