I bought an 1805 and an 1806 from an eBay seller Aug 25 and they came today – exactly two weeks. The 1805 and 1806 have extra features including a timer and a number of extra instructions. I’m looking forward to integrating them into an olduino and taking advantage of them in the compiler.
As an example, these have a single instruction for call and return where on the 1802 we make call and return routines as separate routines each with a dedicated program counter register. The 1805/6 SCAL and SRET instructions do the same work behind the scenes but they take a total of 18 cycles instead of 25 and they free up registers 4 and 5.
from the datasheet