[throwaway152321]

Do you have any insights on how power was delivered to these circuits? Maybe it's done in the metal layers that were dissolved? Also, is it correct that there is no on die capacitance surrounding these circuits?

Thanks for the great article.

[kens]

The 8087 has one metal layer, which makes power distribution more challenging. You want to keep power distribution in the metal, so for the most part the pattern is two interdigitated trees for power and ground. There are a few places where the lines need to cross, which is accomplished with a short polysilicon connection underneath. The two clock lines are also kept in metal whenever possible.

The die photo at the start of the article shows some of the power distribution (the thick white lines around the edge and through the die). I have a close-up shot of the adder's metal layer in the article, showing the thick power and ground metal lines that run next to the adder.

As far as capacitors, there are some capacitors for specific things, but no decoupling capacitors. I think the capacitors are mostly to tweak the timing, if a signal needs to be delayed slightly.