Thanks, Greg!

It turns out that your memory isn't far off! The actual rules do limit your drilling as to both location and size.

Size? The holes can not be larger in diameter than 1/3 the actual depth of the joist. For a 2x10, that would mean a hole no larger than 3-5/32" diameter.

As for location:
1- You are not allowed to drill in the middle third of the span at all;
2- No part of the hole can be within 2" of either edge of the joist; and,
3- Maybe most often overlooked - no part of the hole can be within 2" of another hole (or edge of a notched area).

I want to thank those -I did get some PM's- who provided the information. The source is IRC 502.8.1 ... that is, the 'residential code.'

Please note that these are the rules for "sawn" or dimensional lumber. That is. 'ordinary wood.' The rules are very, very different for LVL's, glulams, TJI's, and any other form of 'manufacturered' wood. It also matters whether the wood is being used as a truss, a joist, a rafter, or a stud.

I'll say it again: electricians need to know more than just the electric code.