Charles.......
The billions (if there are indeed that many) of chips with internal oscillators are not being built with a pair of 7404 or similar type of inverters. The onboard "inverter" is a CMOS type with high impedance input so that a feedback resistor of megohms size may be uesed. I can also comment that the chip designers have done much work to make the circuitry between the X1 and X2 pins of todays parts be much optimized for use in a crystal oscillator configuration in a manner that does not overdrive the crystal.

You may choose to see also the posting made by Kai. He alludes to the fact that some chip makers may even include the series resistor for the crystal onboard the chip. I have not verified that this is indeed the case except that it would be clear that Motorola does not put it onboard some parts. (I referred to the GP32 in last post wherein they recommend a 330K resistor outside the part). From what I can see is that if a vendor should choose to put the series resistor onboard then they will also put the inverter feedback resistor onboard. Both resistors onboard have the advantage that the off board circuit only require two caps and the crystal. If you use the Motorola GP32 scheme then there is a little more flexibility in configuring the oscillator to the crystal and PC board characteristics. (I happen to like that flexibility).

There was a day in times gone by when processors were made of NMOS logic. Sometimes manufacturers would equip these parts with X1 and X2 pins. It was not uncommon that these circuits did not work well and it was necessary to use an external oscillator circuit to obtain a stable clock for the board. In his frustration the digital engineer using an NMOS processor would often turn to the dual inverter type oscillator circuit to get his board going. (Sometimes even using a couple of spare inverting gates on the circuit board)!! This could have been the beginnings of the wide spread use of the troublesome circuit.

In all of the communications that I have posted here I have not discouraged the use of the onboard type of oscillator on any modern microcontroller, RTC chip, or other type of chip. I have discouraged the use of the dual inverter type circuits using the old fashioned designs with bipolar logic gates wherein a low valued feedback resistor is used. I feel that you are incorrect in accepting the old style dual inverter circuit out of hand just because the onboard circuits show an "inverter" in their equivalent circuit diagram. That is a leap that should not be made.

Michael Karas