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CPUShack
Joined: 16 Jun 2003
Posts: 34259
Location: State of Jefferson, USA
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 Posted: Tue May 30, 2023 1:29 am Post subject: CPU Shack: Rare Cyrix Cx486S-40 w/ Cx487S in interposer |
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This is a rare early Cyrix 486 CPU with the Cx487S embedded in the interposer/adapter (since the Cx486S did not have one on die)
Very good condition - Both are dated 1993
$125 sticks it in your box
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Bator
Joined: 28 Oct 2013
Posts: 1285
Location: Russia / Yakutia & Siberia
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| Posted: Tue May 30, 2023 2:11 am Post subject: |
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For me piease
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stamasd
Joined: 05 Jun 2014
Posts: 1311
Location: Connecticut
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| Posted: Tue May 30, 2023 5:42 pm Post subject: |
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| I'll be honest, I never heard of the Cx487s. |
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feipoa
Joined: 08 Mar 2011
Posts: 553
Location: Canada
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| Posted: Tue Jul 04, 2023 2:15 am Post subject: |
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| stamasd wrote: | | I'll be honest, I never heard of the Cx487s. |
And apparently, neither did many motherboard manufacturers because very few boards will run properly with this CPU.
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Williac
Joined: 25 Feb 2022
Posts: 933
Location: Canada
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| Posted: Tue Jul 04, 2023 7:34 am Post subject: |
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Wait, so how did this one work? With the 486SX, DLC, etc, didn’t the FPU take over as the full blown CPU?
Does this one just link in the mathco function with that tiny chip on the bottom?
Would that tiny chip be just the floating point part of a 486DX? |
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RetroTechBytes
Joined: 01 Apr 2021
Posts: 5
Location: USA
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| Posted: Tue Jul 04, 2023 10:02 am Post subject: |
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| Williac wrote: | Wait, so how did this one work? With the 486SX, DLC, etc, didn’t the FPU take over as the full blown CPU?
Does this one just link in the mathco function with that tiny chip on the bottom?
Would that tiny chip be just the floating point part of a 486DX? |
More or less, yes.
The Cyrix 486S is essentially a Cyrix 486DLC with 2kb of L1 cache. The L1 is unique in that it offers a “Burst WriteBack” mode, but few boards properly support this, let alone support the chip itself, as Feipoa mentioned.
The Cx487S is indeed the 387 math-co. It just sits on a small dingus/interposer instead. It’s slower than the 486DX’s setup, but this upgrade allows the M6/Cyrix FasCache to “become” a 486DX of sorts. This is also a configuration that doesn’t work on all boards. Many that support the M6 by itself cannot handle the Cx487S.
It’s a neat chip, but Cyrix really designed a weird one… |
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cvandijk
Joined: 21 Jul 2016
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Location: Netherlands
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RetroTechBytes
Joined: 01 Apr 2021
Posts: 5
Location: USA
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| Posted: Tue Jul 04, 2023 10:34 am Post subject: |
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Mine lacks this too... Strange stuff, but not surprising given that the 486S is kind of a limited-run/cobbled-together product. |
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Williac
Joined: 25 Feb 2022
Posts: 933
Location: Canada
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| Posted: Tue Jul 04, 2023 10:56 am Post subject: |
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| Very cool. That is one of the strangest piggyback designs I've seen for a modern chip. |
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feipoa
Joined: 08 Mar 2011
Posts: 553
Location: Canada
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| Posted: Tue Jul 04, 2023 2:49 pm Post subject: |
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My interposer is also without U3. I suspect U3 helped with compatibility. The model printed on the bottom of my unit is 168C, while the one shown above is 168D.
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