PPC PDS Card
The Apple PPC PDS card is built around a 66MHz PPC 601 processor. This processor runs at double the frequency of the computer it is installed in. You cannot clock chip the PPC PDS card itself, but if the motherboard of the computer it is in is clock chipped, then the PPC PDS card will run at double the new frequency. Although, for example, a Quadra 800 can often be clock chipped to 42MHz, a Quadra 800 fitted with a PPC PDS card will not work at 84MHz. The max for the card itself is typically around 76MHz. See the table below for a list of all the applicable machines.

Machine Max Oscillator Max Speed
C610 14.2857MHz 57.1428MHz
C650 14.7456MHz 58.9824MHz
C650-mod 19MHz 76MHz
Q610 16.96MHz 67.84MHz
Q650 19MHz 76MHz
Q700 74MHz 74MHz
Q800 19MHz 76MHz
Q900 74MHz 74MHz
Q950 80MHz 80MHz

If you accelerate one of these cards, you should put some extra cooling device(s) on the giant heatsink unless you use it as a frying pan to cook on. Two fans mounted on extruded heatsinks and mounted on the card work wonders (no more burns when you pull out the card).

I was just recently made aware of a wonderful trick for PPC PDS card users who never switch back to their 68040 processor. If you pull out the 68040 (be very careful, and take your time), your PPC PDS card will be able to run at slightly higher frequencies without the video artifacts that show up when the 68040 is in place at those frequencies. I have seen this in C650-mod and Q800 machines where the PPC PDS cards now run at 79MHz without any video artifacts. I am extremely curious about what will happen if this is tried in a C610 or Q610. If someone gives it a shot, please drop me a line.

I keep getting e-mail from people looking for one of these cards, so I hope this helps. The cards were discontinued several years ago, so they can probably only be obtained as used hardware. If I were looking for one I'd try the back of some of the Mac magazines, or maybe MacResQ or Pre-Owned Electronics Inc.