Intel 4040
An enhanced version of the Intel 4004, adding 14 instructions, larger (8 level) stack, 8 kbyte program memory and interrupt abilities (including shadows of the first 8 registers). The 4040 was similar to the Intel 8008.
MegaLexica
An enhanced version of the Intel 4004, adding 14 instructions, larger (8 level) stack, 8 kbyte program memory and interrupt abilities (including shadows of the first 8 registers). The 4040 was similar to the Intel 8008.