The 601 card relies on the 040's crystal. Going from Appendix A in the cards documentation, In a 950 it operates at 66mhz. On the Centris 610 it's a measly 40mhz. At the time of print the 840 wasn't released but it makes sense that the card is running at 80mhz mind you it might be running hotter than usual since it's seeing a 14mhz overclock.