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ST Microelectronics 486DX2 is (technically) a Cx486DX2 CPU ?

Peter z80.eu

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Is a ST Microelectronics 486DX2 technically a Cx486DX2 CPU ? And if yes, what (DOS) utility can I use to enable the WB Cache ?
 
Thomson CSF was one of the fabs used by Cyrix for their CX486 line. Thomson's semiconductor operation was eventually merged with SGS to form ST Microelectronics. Because Cyrix was a fab-less operation, one of the inducements to get others to produce their chips was a pretty generous license for the core logic and ST Micro inherited that. ST used the Cyrix core in several products, not just the 486 chips throughout most of the 1990s.

AMD was also a fab source for the Cyrix 486-family chips, but went its own way with the K5 to compete with Intel's Pentium.
 
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Chuck, you're 100% right, but my main problem was getting an utility program to enable or disable a feature of the CPU (Cyrix, ST, TI variants of the Cx486DX CPU), because the mainboard I was using got no Level 2 Cache (no SRAM Cache on the board itself, even no sockets for the SRAM). So my idea was to compensate the lack of SRAM with the Write Back Cache feature of a Cyrix version of the 486. The board itself does not support Vcore less than 5V, so the only possibility was to look for Cyrix/ST/TI variants of the 486DX2 (which still uses 5V, not 3.3/3.45V).
 
What a pity, nobody answered. But I've found a utility program here: https://www.dosreloaded.de/Software/simtelnet/dos/sysutl/5x86c2.zip
It's not exclusively for the Cyrix Cx486DX2, but works for it, too.
Unfortunately it's not working (utility which is included in "5x86c2.zip"), instead, as a last advice, for Cx486DX2 (and licensed, similar ST and TI processor), it is working with "ctchip34.zip", can be downloaded here: https://ftp.gwdg.de/pub/magazine/ct/ctsi/ctchip34.zip (it's a software from a well known german Information Technology magazine).
A small utility which works too, can be downloaded here : https://github.com/karcherm/cx486wb (must be assembled/compiled first). Both, ctchip34 and wbon (and wboff) are definitely working for the Cx486DX ones.
I am satisfied with the results, because if you measure it with a (DOS) benchmark, it significantly accelerates the processing time (Write Back Cache + BTB, see also Cyrix-5x86_Register_Enhancements_Revealed.pdf )
 
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