And they're drop-in replacements for the original.

The discussion of replacement technology has little to do with "clinging to the past." If one has a working system and doesn't wish to redesign and replace the entire system, using modern upgrades that "fit" is an attractive option. That's the reason I'm fascinated with the Maxim/Dallas DS89C4x0 series.

If one wants to do modern things in an older setting, these parts allow that. You can stretch the external bus cycle to make it able to talk to devices too slow (within limits) for the system clock, and it will double or quadruple the input clock if that's necessary in order to meet performance requirements without changing external system timing. One does have to thik about how the MCU and the system work. It may even be necessary to insert NOP's to allow for bus-recovery time.

There are plenty of reasons for using old products with an upgrade. If a board "fits" the application it's supported for years, or even decades, the ability to add functional capability without a complete board respin, particularly in the case of a one-off upgrade, there's no need to perform major surgery.

If you can't do the job without replacing a circuit board, well, then you have to replace it, but if it can be done by simply replacing the MCU, that's easier and some would consider it "better."

RE