My UMC U5SX 486-33F: Does Windows 98SE Detect It as a Pentium MMX? (Computerized Start™ Live)

Описание: You've probably heard of Intel and AMD processors, as both manufacturers are still in business today. If you've been into computing long enough, you've probably also heard of Cyrix. All three companies made 486 processors for Socket 1-3 systems.

But did you know that UMC also made 486 processors? No? That partly might be because Intel sued patent infringement, and as a result of the settlement of the case, UMC had to withdraw their processors from the US market. That might also be because they only made 486SX-era processors, not leaving a huge window for sales in other markets; Wikipedia mentions that they did have a clock-doubled version in production, but only engineering samples existed.

Speaking of Wikipedia, someone has added a claim with no footnote or citation:
"Due to an error in the microcode, Microsoft Windows 98 Second Edition identifies some processors as an Intel Pentium MMX which could cause the operating system and software running within it to crash or exhibit undefined behavior."
(https://en.wikipedia.org/wiki/UMC_Gre..., accessed December 30, 2025)

To which I have to say, "[citation needed]".

Since I now have a UMC Green CPU, specifically the UMC U5SX 486-33F, I can actually try to put this to the test... or all the Windows installs will put me to the test! We'll start with Windows 95 as a control, then upgrade to Windows 98 [First Edition], and finally attempt the update to Windows 98SE.

For science, and #DOScember! (Windows 9x is basically a GUI running on top of MS-DOS.)

Will earlier Windows versions also show an incorrect processor identification? Will Windows 98SE detect my UMC 486 as a Pentium MMX? Or will I have trouble installing Windows 98SE on this unsupported system configuration? You'll have to watch to find out!

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