[PIC] Chip Speeds?

I'm not sure where you are reading that they "don't even bother" but the (maximum) speeds ARE printed on the chips themselves. I have a 16F877-20/P right next to me. The datasheet section on labelling the 16F877 shows the speed rating in the part number as well.

Random aside: The 16F877 and 16F877A are slightly different chips.

The PIC16F877 04/P is a msot of valid part number. It is the 4MHz version of the PIC16F877 in a plastic DIP. There should be at least another letter telling you the temperature grade. There is also a

The PIC16F877A-I/P is also a valid part number. It is the "A" revision of the PIC16F877. There is only one speed grade available,

Go to Microchip's web site and you can read the revised data sheet and find out the differences between the chips.

I believe both parts are in production but the PIC16F877A is newer and probably recommended for new designs. In nearly all cases you can transition from the older silicon to the newer. Sometimes there are small differences that require code or hardware changes. Read the data sheets and errata on Microchip's web site.

Dont' forget that for a 20 MHz PIC, the actual instruction rate is 1/4 that:

Leon

The PIC16F877 is a different chip from the PIC16F877A. Probably the former comes in speed grades and the second one doesn't, I've not looked.

Microchip don't automatically cancel the old version when a new one comes out, they continue to supply it (usually it costs more, so there is some incentive to convert) as long as there is enough demand for their processes.

You have to pay attention to the differences- which include analog type issues, programming algorithms and similar stuff. You can't just automatically sub an A part for the previous part.

Best regards, Spehro Pefhany