Yes, a good idea would to wash the chip in nitric acid to dissolve any copper and silver away, then in aqua regia to remove the gold. You could also take that powder I ended up with and wash that in nitric. Either way, without doing that magnesium drops all the metals dissolved.
This was a very old ceramic chip, so there was not a whole lot of other metals on it.
Sodium metabisulfate is a better dropping reagent and is more commonly used. It is more selective and cheaper. I have had some trouble with it and as I said had no intention of making money so I just used magnesium metal.
Only CPUs contain recoverable gold as far as I'm aware. This will not recover gold from your HDD, motherboard, or any other component.
The HCl I purchased at Home Depot. The nitric acid was purchased from Elemental Scientific, and the bottle the nitric acid is stored in was purchased from HMS Beagle.