Hi, I just watched your video where you upgraded the 486SX-16 with the kingston turbochip, and I was entriqued with the doom results after the upgrade. You thought the most likely culprit here was the ISA videocard, however I played doom with that very same ET4000/AX and found it to be running smooth as silk even on intel 486SX-33... But I also kept using that card through several upgrades including an IBM DX/2-80"Blue lightning"(manufactured by cyrix), and yes, the AMD 5x86 133Mhz/PR75. I was using the 1MB version of ET4000/AX, and found capable to be running early SVGA games such as 7thGuest, Under a killing moon, Wing Commander 3 and 4.. I would say the speed or capacity of the motherboard onboard cache, or the memory access time is the bottleneck, All that hardware and sold it to a friend 25 years ago and he threw it out about 20 years ago, so I can't replicate it. But doom should run a lot faster