question on fpus for 386 \ VOGONS

question on fpus for 386

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First post, by noshutdown

Posted on 2017-12-13, 02:10

noshutdown Offline

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so i have read the lengthy article "EVERYTHING YOU ALWAYS WANTED TO KNOW ABOUT MATH COPROCESSORS", which was written in 1993. it said that the cyrix fastmath 83c87 was both the fastest and the most accurate in the 387 class, save for the less compatible weitek3167. however, i found that cyrix and iit had since released "487dlc" and "4c87dlc" which weren't covered by the article. were they new designs with 486 class floatpoint performance(just like the rapidcad), or simply a rebrand of the old model to indicate that they were designed to work with the 486dlc?

also which is the best 387 emulator? the article named frank387 and q387, but neither performed very well, they simply crashed in some tests and gave very inaccurate results in others. are there any other choices? and do they work with win95?

Reply 1 of 3, by fitzpatr

Posted on 2017-12-13, 06:37

fitzpatr Offline

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There was another thread here on Vogons where someone made mention that there was no difference between the 3c87 and 4c87 coprocessors performance or otherwise. I believe that they are completely interchangeable. Coincidentally, I just purchased an IIT 4C87-40 yesterday.

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Reply 2 of 3, by jaZz_KCS

Posted on 2017-12-13, 11:06

jaZz_KCS Offline

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I recently purchased two IIT 3C87-33 coprocessors. One is running next to a 386-SX20, and one alongside a 386-Sx16.
I knew that they can run at lower speeds as they do not run in full speed (33Mhz) in either of those machines. But I didn't know that 4c87 and 3c87 were interchangeable as well 😖

Reply 3 of 3, by Anonymous Coward

Posted on 2017-12-13, 12:26

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I always assumed that the "87DLC" FPUs were just rebrands of the 387 FPUs, but who really knows. What we do know is that they perform pretty much the same, but it's possible there are bug and compatibility fixes. Unless we find some company memos or contact a former employee we'll likely never know for sure.

The rebrand definitely made sense though, because if you bought a 486DLC then adding an FPU might get confusing.

"Will the highways on the internets become more few?" -Gee Dubya
V'Ger XT|Upgraded AT|Ultimate 386|Super VL/EISA 486|SMP VL/EISA Pentium

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