Ok, I will try to descript some of my memories. At that time I had an XT with 4.77MHZ and a "turbo" switch where the CPUs go to 10MHZ. We are talking about rea

Ok, I will try to descript some of my memories. At that time I had an XT with 4.77MHZ and a "turbo" switch where the CPUs go to 10MHZ. We are talking about real power here and a 30MB HD Seagate. A lot of games/programs run ok with only 640 at that time. But graphic ones and heavier ones need more memory as 1MB or 2MB. Remember that time 1MB was a serious investing or cost. So what we used to do at that times: Several configs.sys and autoexec.bat for each application. Eg.: 1. Boot with CD-Rom drivers; 2. Boot with CD-Rom drivers and others; 3. Clean Boot So I had to choose how to boot my PC before choosing the boot menu, and each menu has its configuration. The more drivers/configs more options becoming an exponential function. So later came Qemm[1] that optimize all options for best scenarios (more free under 640kb or higher mem free). That was a game changer. There were several details, but that was it. Ask me about stacked or other techniques from that time if you are curious :) [1] - https://en.wikipedia.org/wiki/QEMM https://en.wikipedia.org/wiki/QEMM