Information about an unknown IC

On 2022-Feb-24, at 8:29 AM, Clemar Folly via cctalk wrote: A search shows this question was posted over here, with a picture: https://atariage.com/forums/topic/331769-unknown-cart-ic-please-i-need-some… It looks like a home-made board for a plug-in ROM expansion for we-are-not-told. The "TB 759933" is 14-pin DIP, dated coded 7226, has a house number of "239 2100", but it's on a board with a 27256 from 1985. It looks like somebody hacked up this board with on-hand parts. 60 seconds of reverse-enginerring from the limited view in the picture suggests it's likely involved in the address decoding to select the on-board EPROM. The 759933 interconnects with a 74LS10. The LS10 appears to have connections to the chip-select and output-enable of the 27256 EPROM. TB 759933 is not a standard TI number but TI sometimes identified parts they were second-sourcing by embedding the original number in an expanded number. So a guess is this is a 933 DTL dual 4-input (AND function) expander, being used not-strictly-correctly to drive a TTL input. The 933 should be basically 2*4 diodes. A complete reverse-engineering of this trivial board would likely explain the overall intended function.