Pentium FDIV bug - In Pentium Overdrive too?

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Trogdor



Joined: 26 Mar 2003
Posts: 166
Location: Denver, Colorado

PostPosted: Sun Jun 29, 2003 12:13 am    Post subject: Pentium FDIV bug - In Pentium Overdrive too? Reply with quote

I was just wondering, did Intel ever manufacture Pentium Overdrive processors that like their early more advanced brothers, were affected by the FDIV bug (flaw)?

If you don't know or remember, Pentiums can be tested for this flaw by doing certain mathematical calculations (even in Windows Calculator in scientific mode), such as:

4195835 - ((4195835 / 3145727) * 3145727)
If the calculation does not return zero, then the flaw is present. I don't own any Pentiums, so I can't tell you what the computer will give as the answer (if someone could try it and tell me, that would be great).

Intel started manufacturing fixed Pentiums in November 1994, I think.

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Trogdor



Joined: 26 Mar 2003
Posts: 166
Location: Denver, Colorado

PostPosted: Mon Jun 30, 2003 1:02 am    Post subject: Reply with quote

Update: After searching in Google, I found that the flawed answer is: 256
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gshv



Joined: 01 Feb 2003
Posts: 7898
Location: Fairfax, VA USA

PostPosted: Mon Jun 30, 2003 9:12 am    Post subject: Re: Pentium FDIV bug - In Pentium Overdrive too? Reply with quote

I think Intel started to manufacture overdrive processors in 1995 - after the FDIV bug was discovered, so they shouldn't have the FDIV bug.

ast286 wrote:
If you don't know or remember, Pentiums can be tested for this flaw by doing certain mathematical calculations (even in Windows Calculator in scientific mode), such as:

4195835 - ((4195835 / 3145727) * 3145727)
If the calculation does not return zero, then the flaw is present. I don't own any Pentiums, so I can't tell you what the computer will give as the answer (if someone could try it and tell me, that would be great).


I found very interesting graph showing how the FDIV bug affects 4195835 / 3145727 division:
http://www.ku.edu/cwis/units/IPPBR/pentium_fdiv/pentgrph.html

Gennadiy
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Trogdor



Joined: 26 Mar 2003
Posts: 166
Location: Denver, Colorado

PostPosted: Mon Jun 30, 2003 12:50 pm    Post subject: Reply with quote

I don't know; I am looking at Grampa's site and I see a DX20DP66 that would have fit in the time frame for the FDIV bug, but I don't know anything about these, whether or not they would have Pentium instruction sets, and if so, if the FPUs are flawed.

I too saw that web site with the graph - and I saw another similar graph on a different website that shows 3 triangular depressions which progressively decrease in size. I can't find it again, or I'd put up a link. Sorry.

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gshv



Joined: 01 Feb 2003
Posts: 7898
Location: Fairfax, VA USA

PostPosted: Mon Jun 30, 2003 11:51 pm    Post subject: Reply with quote

ast286 wrote:
I don't know; I am looking at Grampa's site and I see a DX20DP66 that would have fit in the time frame for the FDIV bug, but I don't know anything about these, whether or not they would have Pentium instruction sets, and if so, if the FPUs are flawed.


DX2ODP66, as well as other DX2xxx and DX4xxx overdrive processors are based on 80486 technology, and they do not have FDIV bug.

Gennadiy
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