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Installation and jumper info for cyrix 5x86-133p/4x

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First post, by pcsintheup

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I found this cyrix 5x86-133p/4x in my bin of parts in the basement. I can find no installation manual and nothing on ebay (ill often read retail boxes on ebay to get a clue). It has this weird mediator/socket adapter with jumpers. Hoping to get info on using it in my 486 dx2 66. Can I just drop it in? It says 3.6 volts and of course my 486 is 5 volts. Then theres the jumpers. This must be rare as I can find zero info other then speed tests that show it spanking normal 486’s. Thanks for any info.
Oh any idea on its worth? Cant find any past sales even.

Reply 1 of 6, by PD2JK

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Look here, the first one:

https://www.ardent-tool.com/CPU/486_interposer.html

i386 16 ⇒ i486 DX4 100 ⇒ Pentium MMX 200 ⇒ Athlon Pluto 700 ⇒ AthlonXP 1700+ ⇒ Opteron 165 ⇒ Dual Opteron 856

Reply 2 of 6, by Many Bothans

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Nice find, the Cyrix 5x86-133 GP is really uncommon.

  • Zenith Z386SX-20, 8MB FPM, Video 7 1024i, Unhoused
  • AOpen AP43, Am5x86-133@160, 1MB L2, 128MB FPM, Stealth III S540 32MB Savage4, SB32
  • ITX-Llama, 3Dfx V3
  • Asus CUV4X-E, P3-933, 512MB PC133, Hercules 3D Prophet II MX 32MB, SB Live!

Reply 3 of 6, by pcsintheup

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@pd2jk wow thanks thats exactly what Im looking for

Reply 4 of 6, by ChrisK

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Isn't that one of the rarest 486 CPUs?
Definitely worth a bit! Particularly in that condition.
You shouldn't forget to put a heatsink/fan on it.

RetroPC: K6-III+/400ATZ @6x83@1.7V / CT-5SIM / 2x 64M SDR / 40G HDD / RIVA TNT / V2 SLI / CT4520
ModernPC: Phenom II 910e @ 3GHz / ALiveDual-eSATA2 / 4x 2GB DDR-II / 512G SSD / 750G HDD / RX470

Reply 5 of 6, by kixs

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This rare CPU is on a pretty common adapter. The adapter is only needed when installing the CPU on an older 486 motherboard that doesn't support 3-4V and usually these don't have jumpers to set the multiplier.

If you have a newer 486 with PCI slots. You don't need the adapter at all. You can remove the CPU and set the jumpers on the motherboard for Cx5x86.

Visit my AmiBay items for sale (updated: 2025-10-29). I also take requests 😉
https://www.amibay.com/members/kixs.977/#sales-threads

Reply 6 of 6, by debs3759

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I've seen them sell for upwards of $500 without the interposer. Very hard to find.

See my graphics card database at www.gpuzoo.com
Constantly being worked on. Feel free to message me with any corrections or details of cards you would like me to research and add.

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