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Old 07-02-2020, 09:43 PM   #1
japlytic
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Default Pentium FDIV bug did not affect the K5

Based on available information, the Intel Pentium FDIV bug did not affect the AMD K5 compatible - it seems that AMD implemented things a bit differently to Intel at the time (and still does as of today).

Has it also affected other Pentium-compatible processors? So far, I've seen Pentium-compatibles (code and pin) not just from AMD, but also from ST/IDT/IBM/Cyrix.
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Old 07-02-2020, 10:17 PM   #2
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Default Re: Pentium FDIV bug did not affect the K5

The pentium pro was the last affected by this.
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Old 07-03-2020, 02:37 PM   #3
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Default Re: Pentium FDIV bug did not affect the K5

https://en.wikipedia.org/wiki/Pentium_FDIV_bug

I would imagine most of the defective chips have been replaced or disposed of by now. I never had a chip with FDIV - my P100 and PPro (socket 8) chips do not have the bug, nor does my K6-233.
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Old 07-03-2020, 07:37 PM   #4
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Default Re: Pentium FDIV bug did not affect the K5

I only heard of the "FDIV" bug on consumer Pentiums, on 100s and before.

133s and 166s not affected, according to Intel, IIRC.

It sure gives me the strange feeling that Intel rushed the chips for the general consumers, hoping that people won't find out!
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Old 07-04-2020, 04:28 PM   #5
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Default Re: Pentium FDIV bug did not affect the K5

Quote:
Originally Posted by RJARRRPCGP View Post
I only heard of the "FDIV" bug on consumer Pentiums, on 100s and before.

133s and 166s not affected, according to Intel, IIRC.

It sure gives me the strange feeling that Intel rushed the chips for the general consumers, hoping that people won't find out!
Yep. Only on the older ones along with some of the 486OD's

https://en.wikipedia.org/wiki/Pentiu...ffected_models
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Old 07-04-2020, 04:35 PM   #6
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Default Re: Pentium FDIV bug did not affect the K5

yea it looks like intel wanted to be the first to rush out the world's first 100 mhz chip. similar to how later, there was a 1 ghz rush between intel and amd to get the world's first 1 ghz chip. intel repeated their folly again with the spectre and meltdown bugs to boost performance. a leopard never changes its spots!
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Old 07-04-2020, 05:51 PM   #7
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Default Re: Pentium FDIV bug did not affect the K5

That bug looks worse than Spectre and Meltdown.
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Old 07-04-2020, 07:13 PM   #8
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Default Re: Pentium FDIV bug did not affect the K5

TBH meltdown/spectre and their related bugs are "unintended use" of the CPU and there was really no way to know about it until one really thinks about it. The computer never does anything "wrong" -- just discloses information it shouldn't. Unintended consequences - they never described this behavior explicitly, rather it was behavior that was explicitly undefined...until it was noticed it was stealing information.

The F00F bug was pure stupidity (though easily worked around), and FDIV was also something they should have caught but didn't. Both of these are "doing the absolutely wrong thing" and "not as described" behavior.

I suppose intel deserves the big target painted on its back for being the biggest...
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