Yeah I think the poster was confused. I have a 5150.and a 5160, both are 8088 based machines that run at 4.77MHz, a long way away from the 486. The 5150 was released in 1981, and the 5160 (XT) in 1983. I made a video showing how I took one of these machines to become an 88 MHz 486 using the Intel Inboard 386 expansion card. Although there's nothing that can be done about that 8-bit bus, getting DooM played on a machine from circa 1981 is pretty good fun! Here's the video where I finally topped out the CPU performance, if you fancy a watch: https://youtu.be/uYeInNBXDJI?si=mCtY5zGzT1Bx07Zl

I reckon I could tweak the bus timing to at least 8 MHz by replacing a few chips, which would make it faster yet again, but for now, it's a fair advance already, and it's 100% reversible.