There were lots of 486 & Pentiums equipped with CDROM drives, ATX & software power didn't really become a thing until 686/Pentium II machines came out. My first 'ATX' machine was in a baby AT case - An Amd K6-2/450 on an MSI super socket 7 motherboard. It was an upgrade from a Pentium 166MMX, and I had to use the reset button as a power button. The original (actual on/off, not pushbutton) power switch left with the AT power supply.