There are no specific documents on it. It's in the MCS650x data sheet. It's just a 6502 die in a smaller 28-pin DIP package with not all of the pins bonded out. Specifically, A12 through A15, RDY, /NMI, SYNC, SO, three NC pins, and one Vss pin are not available. The pinout is: /RES 1 28 Ph2 out Vss 2 27 Ph0 in Ph1 out 3 26 R/W /IRQ 4 25 D0 Vcc 5 24 D1 A0 6 23 D2 A1 7 22 D3 A2 8 21 D4 A3 9 20 D5 A4 10 19 D6 A5 11 18 D7 A6 12 17 A11 A7 13 16 A10 A8 14 15 A9 I'm looking for the Synertek 6516 data sheet, and Synertek technical notes 34 and 40. The 6516 was to be a 16-bit extension of the 6500 family, years before the 65802/65816. Synertek published a data sheet in mid 1978, but the part was never put into production.