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Inside the Pentium II Math Bug

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Dr. Dobb's Journal August 1997: The Chronology of Dan-0411

Dr. Dobb's Journal August 1997

The Chronology of Dan-0411

By Robert R. Collins

Friday, April 11th, 1997. "Dan" sends me e-mail, saying he thinks he's discovered a math bug in the Pentium Pro. Dan doesn't have the means to write assembly-language source code to verify the bug, so he contacts me. Initially, I decide not to get involved because this could be a real hot potato. I've already had my problems with Intel and I don't want any more -- especially if this turns out to be a serious bug. My web site receives a typical 31,258 hits on this day.

Monday, April 21st, 1997. After more pressure from Dan and discussing the possible consequences with friends, I decide to write the source code that determines whether or not Dan has found a bug. Intel stock closes at approximately $140 per share. My web site receives 29,795 hits.

Tuesday, April 22nd, 1997. I send Dan confirmation that he has found a bug in the Pentium Pro. I also tell Dan that I have access to a Pentium II, and the bug also appears in Intel's newest microprocessor. Intel stock closes at near $142 per share. My web site receives 30,707 hits.

Tuesday, April 29th, 1997. I post a message to comp.sys.intel saying that I think a new math bug existed in the Pentium Pro and Pentium II. (I expected my message would be largely ignored as a "troll" for a flame fight. As I shortly found out, mixing the words "MAJOR," "FLOATING POINT BUG," and "PENTIUM PRO" in a message subject line is a volatile combination of words.) Intel stock closes near $150 per share. I receive 35,720 hits.

Wednesday, April 30th, 1997. An Intel representative calls me on the phone wanting any information I can to give him. I tell him that I'm pretty sure it's a bug, but that I don't have Dan's permission to give him any further information. Intel stock closes near $154 per share. My web site receives 37,959 hits.

Thursday, May 1st, 1997. I start getting strange phone calls about the bug. The first comes from an "investor" with a British accent who only cares about the authenticity of the Usenet report. After I try to explain the possible insignificance of the bug, he says "I don't care, I'm an investor," then promptly hangs up.

Fifteen minutes later, I receive a second phone call -- this time from a man claiming to be an attorney. He claims to represent clients who file class-action product-defect lawsuits. I don't bite his bait and become suspicious. I ask who his client is and why he's poking around this bug issue. The "lawyer" becomes defensive and refuses to tell me who he works for or to explain his interest in this bug report. Finally, he threatens me with a libel lawsuit if I can't prove that a math bug really exists in the Pentium Pro and Pentium II. I automatically assume that this lawyer is somehow connected with the investor who called me a few minutes earlier. This just couldn't be a coincidence.

Unnerved by the phone call, I call my contact at Intel. He denies that any Intel attorneys are involved. He promises to keep the attorneys off my back. He uses the opportunity to press me for further details about the bug. Again I decline, citing my lack of Dan's permission to give him any more information. Intel stock closes near $155 per share. My web site receives 42,231 hits.

Friday, May 2nd, 1997. CNet reporter Brooke Crothers sends e-mail to ask me for confirmation of the bug report. Crothers doesn't wait for my response, and posts the breaking story on the CNet web site (http://www.cnet.com/).

Intel contacts me one last time before the coming weekend. Again, I decline to give any further information.

At 11:00 PM, I get a call to notify me about the CNet article. I had no prior knowledge of its existence. Intel stock closes near $158 per share. My web site receives 45,272 hits.

Saturday, May 3rd, 1997. With the CNet article published, the threat of a libel lawsuit begins to weigh heavily on me. I know that I must write the bug report or risk legal consequences. I convince Dan that the report must be made public. I decide to post a message on Usenet informing the Internet community that the bug report will be made public on May 5th, at 0900 PST. I send a copy of this message to Intel. The stock market is closed for the weekend. Typically, my web site traffic decreases by 20%. Instead, activity increases as the pressure to publish the bug builds. My web site receives 52,581 hits.

Sunday, May 4th, 1997. I work all day Saturday and Sunday perfecting the article and giving it to various individuals for peer review. I also perfect the assembly-language source code and decide to offer it, as well as binary executable programs, to anybody who wants to detect the bug.

By 10:00 PM, I have packaged the article and source code for publication. Sunday is typically the slowest day at my web site. I usually receive fewer than 20,000 hits. On this day, I receive 39,654 hits.

Monday, May 5th, 1997. I make some finishing touches to the article. I'm finally finished at 0830 PST, just 30 minutes before publication. I send a copy to Intel (before the official publication time).

Even though the 0900 hour hasn't come, reporters are already calling me in my office and on my cellular telephone. I don't give any advance information, yet their articles run before the official 0900 publication time.

Within minutes of publication, e-mail messages start rolling in from various press organizations: CNN, MSNBC, Wall Street Journal, EE Times, CNet, PC Week, and others. Luckily, I forget to take my cellular phone with me and am unable to take their phone calls; thus, they send their interview requests via e-mail. With news of the bug report, web site activity soars. Intel stock closes near $163 per share. My web site receives 349,418 hits.

The bug report goes international. I start getting interview requests from France, Germany, Australia, Japan, and other nations.

Various attempts are made to discredit the bug report or to minimize it.

Tuesday, May 6th, 1997. The bug report shows up in various print publications. The online publications report the bug as a top story, eclipsing Intel's Pentium II announcement.

Reports start surfacing that I'm getting revenge on Intel for its legal action against me. (No legal action ever occurred.) Another report surfaces that AMD is behind the bug report. Another report surfaces that this bug report was calculated to be timed with the Pentium II announcement (even though a rudimentary analysis of the chronology that appeared in the original article would have refuted such claims).

Two industry analysts downgrade Intel's stock from "buy" to "neutral" because of the bug report. After an initial surge in Intel's stock price, it loses five points to close near $162 per share. My web site receives an all-time record of 503,989 hits.

Wednesday, May 7th, 1997. I get a private e-mail from a guy (I'll call Mr. X) who claims that I may have made a mistake in my bug analysis. He claims that the bug may be much more severe than I had originally reported. He also claims to have spoken with me in the week prior, and that he's an investor in AMD, but not selling short on Intel stock. (Strange set of information.) Within minutes, CNet sends me e-mail asking me to confirm this guy's claims. I wonder how CNet got a copy of this e-mail, and become suspicious. CNet claims Mr. X sent them a copy of his e-mail to me.

Intel's stock loses three more points to close under $160 per share. My web site receives 345,531 hits.

Later that night, I call CNet and ask a few questions of my own. I want to know how they learned of this story -- reporting it three days before their competition. They tell me Mr. X tipped them off.

Thursday, May 8th, 1997. I confirm the claims by Mr. X. My original article contained an ambiguous paragraph that minimized the severity of the bug. I fixed the ambiguity and called CNet to confirm Mr. X's claims. By now, I'm a little suspicious of Mr. X, and I wonder if CNet has actually talked to him. They confirm they have, and tell me he's got a British accent. I become convinced that Mr. X is the same investor who called me on May 1st. Both have a British accent and both claim to have spoken to me.

After I confirm the ambiguity in my original report, a second round of press reporting is sparked. Now, everybody's reporting that the bug is more severe than originally anticipated. Intel stock starts to regain some lost ground, closing near $161 per share. My web site receives 262,937 hits.

Friday, May 9th, 1997. I go on vacation...I need to get away.

Intel posts its response after the stock market closes. The bug is much more severe than originally discovered during my analysis.

I get a phone call from a representative of Senator Toricelli's (D-NJ) office in Washington, DC, telling me about legislation introduced in the Senate that I might be interested in (not related to the bug, though). He mentions that my web site is reasonably well known in the Capitol. Intel stock continues to inch back up, closing near $162 per share. My web site receives 234,809 hits.

Saturday, May 10th, 1997. I appear on a computer radio show. Afterwards, life gets back to normal. The stock market is closed for the weekend. My web site receives 120,072 hits. Slowly, my web site traffic returns to normal, though "normal traffic" appears to be more than double the level it was before the bug was reported. My 15 minutes of fame are now over.

-- R.R.C.

Copyright © 1997, Dr. Dobb's Journal

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