[SpeedGeek]

** NEWS UPDATE ** The 74Fx803 clock divider on the A3640 is rated to run at 70 Mhz max! Obviously, your mileage will vary. If you have tried TIMING ADJUSTMENTS ON BOTH DELAY LINES* and are still having problems with this mod try an oscillator in the range of 66 to 74 Mhz and adjust the timing on either delay line. If your 74Fx803 won't run reliably at 80 Mhz you have the options of using a different chip (74F74) or even a clock doubler chip if you really want to get to 40 Mhz. *Your timing @40 Mhz should be within +-5 ns of mine. Otherwise try to reconnect U208 Pin 1 to the cut trace. This part of the mod is only needed for Ramsey to run a 4 clock cycle. Unfortunately, it's also the most timing critical part.

** 2ND NEWS UPDATE **
A datasheet has been uploaded. It would be a good idea to make sure the +5 Volt supply to the A3640 is at least 5 Volts. Another potential problem is skew between Bclk and Pclk. Motorola specifies 9 ns @25 Mhz and gives no spec. @ 40 Mhz. Using the formula 25/40 x 9 gives a calculated value of 5.6 ns. With the 74Fx803 being overclocked it's likely to be right on the edge. A skew problem could easily mislead you to believe your 74Fx803 or 68040 won't run at the desired clock speed! Fortunately, there is a simple cut and jumper mod to compensate for the skew.