http://www.rme-audio.de/english/mac/osxcom.htm
RME updates information on G5 compatibility
All currently available RME interface cards are fully compatible to Apple's new G5 computers. They operate at the reduced voltage of 3.3V, and therefore provide the second notch at the PCI contacts to fit in any PCI-X slot. This is especially true for all PCI cards of the HDSP series, HDSP PCI, HDSP 9652 and HDSP 9632.
Older cards are in many cases not compatible:
Hammerfall (DIGI9636 and DIGI9652) revision 1.5/1.6: These cards have been shipped since June 2000. Until the end of 2002, cards being compatible and incompatible to PCI-X slot computers have been shipped. Unfortunately it is not possible to define the time frame more accurately, nor to list the affected manufacturing dates.
DIGI96 series: Cards which were compatible and incompatible to PCI-X slot computers have also been shipped in the DIGI96 series until the end of 2002. Unfortunately it is again not possible to define the time frame more accurately, nor to list the affected manufacturing dates.
Using one of the above cards in an Apple G5 computer can cause serious damage to both DIGI96 and Hammerfall series of cards, as well as damage the G5. Therefore RME strongly advises to have all cards meeting the above criteria to be checked by RME before using them in a G5. Checking and - if neccessary - modification is done for free by RME's representatives.
Hammerfall (DIGI9636 / DIGI9652) revision 1.1: These cards, manufactured from 1999 to April 2001, are not Mac compatible at all - and thus can't be used in a G5 anyway.
Note: the revision is printed on the PCB. The date time of manufacturing is coded as week/year on the back of the cards, within a copper area (for example 17/01 for week 17 in 2001).