A bit of an update on work to date.
To summarise, replacing the 31ish mhz xtal with a 40mhz xtal kind of works, but no ADB mouse, and there's a fairly predictable bus error after 20 mins of operation after which the machine won't warm boot (it needs a power cycle to come back)
I scored a 40 mhz 030 and 882 off ebay to see if the limitation was the frequency rating of these parts. Swapping the 030 is simple on a socketed motherboard.
Swapping the 882 takes a bit more work. You cut the chipselect trace on the mobo (runs from the GLUE to the CoPro underneath the board). Put a pullup resistor on the 882 to disable it.
Then route the CS line to pin 2 on the PDS connector. This line is unused on the SE30.
Put the 40mhz 882 in the Radius CP card.
This combo works just fine with the 31 mhz xtal, but sadly there is no improvement in the stability when a 40mhz xtal is used. In fact it's probably worse!
So it's back to the drawing board, it appears that something else on the MOBO doesn't like being overclocked.
Next step is to separate the clocks out, feed the VIAs from a lower freq clock and see if it can deal with the waitstates.
I also want to build an oscillator circuit that can be adjusted, and try stepping it up from 32-40 mhz and see where problems start occuring.
Tim
To summarise, replacing the 31ish mhz xtal with a 40mhz xtal kind of works, but no ADB mouse, and there's a fairly predictable bus error after 20 mins of operation after which the machine won't warm boot (it needs a power cycle to come back)
I scored a 40 mhz 030 and 882 off ebay to see if the limitation was the frequency rating of these parts. Swapping the 030 is simple on a socketed motherboard.
Swapping the 882 takes a bit more work. You cut the chipselect trace on the mobo (runs from the GLUE to the CoPro underneath the board). Put a pullup resistor on the 882 to disable it.
Then route the CS line to pin 2 on the PDS connector. This line is unused on the SE30.
Put the 40mhz 882 in the Radius CP card.
This combo works just fine with the 31 mhz xtal, but sadly there is no improvement in the stability when a 40mhz xtal is used. In fact it's probably worse!
So it's back to the drawing board, it appears that something else on the MOBO doesn't like being overclocked.
Next step is to separate the clocks out, feed the VIAs from a lower freq clock and see if it can deal with the waitstates.
I also want to build an oscillator circuit that can be adjusted, and try stepping it up from 32-40 mhz and see where problems start occuring.
Tim