Redherring32 (of OpenTendo fame) has been putting in some research into bypassing the need for a clock capacitor on the 1.6 revision Xbox; unlike the prior models a 1.6 will not boot without it. By removing R7P3 and R7P6 current limiting resistors which go to the positive leg of the clock cap and then connecting 3v3 standby voltage to that same leg, you can remove it entirely and still have a functioning system.