DIY VDP TMS9129NL/TMS9929ANL tester. VDP chip is a video chip from Texas Instruments used in multiple 8-bit home computers (TI-99/4A, MTX, SVI 328, MSX). As far as I see TMS9129NL/TMS9929ANL are pin compatible more on the topic can be found here, but I'm not sure on exact differences, beside the clock (TMS9929 uses 10.6875MHz crystal) and DRAM difference (TMS9929 uses 1 bit chips vs TMS9129NL 4 bit) .
This tester helps you test the chip out of circuit using arduino.