Dear Kevin,
you mix everything together! Load capacitance is what the port and control lines see at their pins, when copper traces running over a ground plane and digital circuitry is connected to them. Assume that an external RAM is connected to the port lines. Then about 5pF of trace stray capacitance and about 5pF per driven input must be taken into calculation, makes roughly 10pF per port line.
If signal routing is extended over a wider board area and if more than only one chip is connected to port lines, then capacitive load increases accordingly. This 60pF limit shows you how much external circuitry you can connect to the port lines of your micro.
Exceeding this limit will increase ground bounce to an unsane value, means signal integrity tends to be eroded and noise margin tends to be violated.

Load capacitance of the crystal is something totally different. The correct name of this capacitance is burden capacitance and is highly needed for the pierce oscillator to work properly. The purpose of burden caps is to add a very defined phase shift to fullfill the 180° criteria for maintaining of oscillation.

In an earlier post I have discussed the importance of these burden caps for proper operation of pierce oscillator. You can find it here:

http://www.8052.com/forum/read.phtml?id=79811

The correct procedure to find the right crystal for your micro is:

1. Determine the right crystal frequency for your application.

2. Use the burden caps suggested by the manufacturer for this frequency.

3. Choose a crystal, which is fabricated for a capacitive load built of (burden capacitance + 5pF gate input stray capacitance)/2, which is about 12...15pF in your case.

This crystal will give you a clock frequency which is nearest to the value stamped on it. Why? Because the manufacturer has taken just this capacitive load into calculation when fabricating your individual crystal.
Other crystals will also work, but not as precisely.

One last hint: Take care that you only use a fundamental quartz, not an overtone one! A fundamental quartz resonates on the frequency stamped on it. An overtone quartz needs a different oscillator circuit to resonate at the frequency stamped on it. But put into the pierce oscillator of your micro you will observe an oscillation at a frequency of only about one third of nominal frequency!

Kai