Yes, the "old standards" are "true" to the '51 '52 difference; however I wanted to state that '51 does not necessarily mean 128. I had a discussion with someone a while ago who insisted that the 80C51RD2 only had 128 bytes of direct RAM since it was a '51. Let us avoid any relation between the number and the memory and just say "check the data sheet"

Happy hollidays,

Erik