This was the system in which the directory logic was formally verified: http://www.sgidepot.co.uk/origin/compcon97_dv.pdf

I agree the author probably made a simple mistake, but it is misleading to people at the "enthusiast" level who then parrot things like this as flamewar fodder. A lot of respect is owed to computer engineers at corporations that are defunct or a fraction of their former greatness (e.g., SGI, DEC, HP).

As a further example, Bob Colwell's book, "The Pentium Chronicles", is a great read and teaches some powerful lessons about how to successfully do engineering in the kind of large organizations that can scale production of a design. But if you take it at face value, the book makes no meaningful attempt to inform the reader that other companies had done Out-of-Order well before P6. It leaves a naive reader with the idea Intel pioneered OOO as well, which is no way true.

I guess I'm just (maybe overly) sensitive to sloppiness and omission leaving an inaccurate impression of the history, especially when it's so easy these days to fact-check.