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Pentium Divider Flaw

wct097

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Feb 28, 2011
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Wait, are you saying you've got the machine that the bug was originally discovered on? I apparently work with a guy who worked with the guy who discovered how the problem was introduced in a logic lookup table of some sort. Apparently my co-worker's previous co-worker was the one who tracked it down enough for intel to actually verify that there was a problem. It all sounds very urban legend to me, but I suppose if you're in the tech industry the odds of running into someone like this are pretty good...

Exactly. That's what it written & signed on the inside of the case at least. Dr. Nicely was a professor at Lynchburg College. I live in Lynchburg, have never met the man, but came across this when my brother was helping his former boss clean out his basement and take a bunch of things to the dump. The former boss, I'm told, was friends with Dr. Nicely.

You know, instead of speculating about this, why not drop the good Doctor an email?. Who knows? He may be interested in getting this system back...

Scored an AT-PS2 adapter today, so I'm going to try to power it up and see what the story is. If it doesn't boot or I can't figure out if the processor was replaced I may drop him an email.
 

Unknown_K

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Checked the loose P60 I have and it doesn't have the FPU bug, the other chips are in systems (One packard Bell and one PS/2 Model 90) so I will check those later.
 

wct097

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It booted up fine. Running Windows 3.1. Don't have a serial mouse, so I could only fiddle with as much as I could get to using the keyboard. Would seem that it no longer has the original flawed chip in it, but that's not surprising. Didn't really expect it to.

IMAG0142.jpg
 

k2x4b524[

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no, but if this is the maching that DID discover the bug, it may have some sentimental value to him. I know if it were me that were in his shoes and i was reading this thread, i may want it back, besides, that hard drive may have some of his original work on it, shoot him a line, nothing bad can come of it short of he's not interested in it anymore, or even worse, he is deceased or something.
 

wct097

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no, but if this is the maching that DID discover the bug, it may have some sentimental value to him. I know if it were me that were in his shoes and i was reading this thread, i may want it back, besides, that hard drive may have some of his original work on it, shoot him a line, nothing bad can come of it short of he's not interested in it anymore, or even worse, he is deceased or something.

I'll drop him an email. I doubt it has a sentimental value to him as I believe it was given/sold to someone else before heading to the dump after a basement cleanout. I don't think it was unintentionally lost or stolen.
 

wct097

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Dr Nicely replied to me and verified the authenticity of the machine. An excerpt from his response:

The flawed processor was swapped out when
Intel sent me a corrected replacement in
early November of 1994. I then donated the
flawed processor (along with a few other
new and corrected ones that Intel sent) to
my employer, Lynchburg College, which they
used to construct new systems at a discount.
A flawed processor from a machine owned by
one of my colleagues in the Mathematics
Department was also donated, after we
swapped one of the new processors into
his system. The two systems constructed
by the College with the flawed processors
remained in service (in the student labs)
for several years. I had a standing offer
during that time of (considerable) extra
credit for any of my students that could
demonstrate an error caused by the flaw
(other than a variation of the ones already
known). Nobody ever collected. I assume
the College eventually junked those two
machines (I retired in July, 2000).

Anyone know what the going price for a flawed Pentium is? Anyone have a non-rare version they'd be willing to part with?
 

Neon_WA

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Anyone know what the going price for a flawed Pentium is? Anyone have a non-rare version they'd be willing to part with?

A ceramic P60 about $20 - 30 (sSpec SX753)
A Gold top P60 about $15 without the word "Processor".. with about $25 (sSpec SX835)

big issue at the moment.. is gold scrappers have pushed prices up
 

wct097

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A ceramic P60 about $20 - 30 (sSpec SX753)
A Gold top P60 about $15 without the word "Processor".. with about $25 (sSpec SX835)

big issue at the moment.. is gold scrappers have pushed prices up

Would you be willing to sell me one of the cheaper 60mhz versions, so that I can install it in this PC to give back to Dr Nicely?
 

Neon_WA

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shipping from Oz isnt cheap.. but I will see what I can pick up on US ebay. I have some CPU lots on the way to my friend in Oregon that may have one in it.
But if not... one will come up soon
 

luckybob

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check my "do you have ocd" thread. I just picked up a huge pile of processors, one my be the s-spec you are looking for.
 

Neon_WA

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the last 2 I got in CPU lots were both uncommon sSpecs.. one worth $50+ the other $100+ and I dont think you want to part with that much

but still keeping my eyes open for a common one
 

Neon_WA

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check my "do you have ocd" thread. I just picked up a huge pile of processors, one my be the s-spec you are looking for.

the machine originally had a P60

and you have 2 SX835s that would do the job. The one with missing print probably his cheapest choice

According to Wikipedia, a total of 39 different s-specs are affected by the bug. See http://en.wikipedia.org/wiki/Pentium_FDIV_bug#Affected_models for a complete list.

dont believe everything you read on Wiki... there are many missing off that list
 

per

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dont believe everything you read on Wiki... there are many missing off that list

Of course, but these 39 are at least known to have the bug. Intel never provided a full list of affected s-specs, so the only way to actually make a complete list is to test every single s-spec CPU of the early Pentium series. This is quite a lot of CPUs, and it would be very difficult for somebody to get every single one.
 

Neon_WA

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Of course, but these 39 are at least known to have the bug. Intel never provided a full list of affected s-specs, so the only way to actually make a complete list is to test every single s-spec CPU of the early Pentium series. This is quite a lot of CPUs, and it would be very difficult for somebody to get every single one.

I am aware of 57 (30 qSpec & 27 sSpec)
so far I have only managed to get a total of 16 for my collection as the rarer ones now go for $400+
 

per

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I am aware of 57 (30 qSpec & 27 sSpec)
so far I have only managed to get a total of 16 for my collection as the rarer ones now go for $400+

Then I would suggest that the tables on Wikipedia should be updated.

By the way, how do you know if one is rare or not? I guess the one I have (SX835 if I remember correctly) is a common one as it already is in the table.
 

wct097

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Turns out that my coworker has a display case with a variety of old processors in it. He thinks two of them are the flawed versions. We're going to check today to see if any of them work and are indeed the flawed variety.

The question is; does an original Pentium need a heatsink & fan? The processor that is installed has one, but it appears to be glued/attached directly to the processor and not readily removable. The chips we have available don't have heatsinks attached.
 

wct097

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Found an SX835 chip that's been in my coworker's office for years in a display case with a variety of other processor chips. Installed in the machine and tested positive as flawed. Going to have to chase down a proper heatsink & fan now. The one in the machine now isn't properly secured.
 

Neon_WA

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Found an SX835 chip that's been in my coworker's office for years in a display case with a variety of other processor chips. Installed in the machine and tested positive as flawed. Going to have to chase down a proper heatsink & fan now. The one in the machine now isn't properly secured.

Good one :) if produced before week 19 1994 it should have the "Processor" marking
most socket 4s only had heat-sink, but one with fan would be better as they run so hot.. but not as hot as the P66
 
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