Windows 7 was made to run on a mere 5MHz Pentium, 128MB RAM and it worked, mostly

It is hard to deny that Microsoft's Windows 7 was one of the most beloved operating systems with many cherished features and some may certainly argue its impact was just as big as those of Windows 95 and Windows XP before it. While support for Windows 7 ended over two years ago, the 2009 OS is still the third most popular with around a 10% market share.

One of the reasons for its popularity was its meaningful system requirements as it could actually ran well on its minimum requirements. All you needed was a 1GHz single-core CPU and 1GB (32-bit) / 2GB (64-bit) system memory. And despite such low requirements, the software was designed to support up to 256 cores/threads in 64-bit mode highlighting that it was pretty forward-looking. Although Microsoft stuck with the same requirements till Windows 10, it is generally never as smooth an experience on the newer much heavier OS.

To test how low one could go with Windows 7, Twitter user and Windows enthusiast NTDEV tried running it on a 5MHz Pentium-S processor - which is 200 times lower than the official requirement - and 128MB of RAM. You may notice in the image below that the Pentium chip is running at 50MHz. NTDEV notes here that the LogonUI refused to load up with anything below that. The 5MHz clock was achieved by editing 86Box's source code, the virtual machine where the test was conducted.

Aside from this, several major modifications were made too. The entire OOBE folder (c:\windows\system32\oobe folder) was deleted and Registry tweaks were made to emulate a "pseudo-OOBE state". The BCD (boot configuration data) was also tweaked so that it booted into Safe Mode even when the "Start Windows Normally" option was chosen. For further de-bloating, the GUI elements were disabled too.

NTDEV successfully managed to boot into Windows 7 Ultimate build 7601 SP1 after around 28 minutes. The system was stable with the WCPUCLK or Real TIme Clock Checker confirming that the system was indeed running at 5Mhz.

Ultimately it was a fun experiment and most people who are still running Windows 7 as their daily driver probably are doing so on much faster PCs anyway. And in case that PC happens to meet Windows 11 requirements, Microsoft says you can certainly upgrade to its latest OS though it would require a clean installation.

Source: NTDEV (Twitter) (1), (2) via Tom's Hardware