I was building a little board with a 20 pin ZIF socket on it and intended it to be able to program either ATTinyX313 or ATTinyX5, connected to a (genuine) Atmel AVRISP MKII programmer.
My problem is (don't laugh) it works! (and it shouldn't).
AFTER I tested it and found that it worked, I then looked over my circuit diagram and what I did on the board. I made an error (the board did not match the circuit diagram) but it works anyway and I can't for the life of me figure out WHY!
Please take a look at the attached sketch.
When an X5 chip is in the socket, it has no ground, but it programs!
When an X313 chip is in the socket, it has no crystal (the fuses are set for EXTERNAL crystal), but it programs!
(click thumb for full size)
The crystal, BTW, is a 10.000 MHz, VCC is 5.0V and pin 10 in red is the X313 ground (not all pins shown for clarity).
I'd appreciate it greatly if someone could tell me why this thing works!