For the OBC-Cube-Polar GPIOs, the “buffer speed” depends on which GPIO group you use (because the 24 GPIOs are implemented in four electrical groups):

Group A – GPIO [1…8] (buffered, 8 channels)

Group B – GPIO [9…16] (buffered, 8 channels)

• These two groups use high-speed logic buffering (ns-class propagation).
• Practically, they support tens of MHz comfortably, and 100+ MHz is typically achievable for light loads/short routing. (The real limit is your loading, edge-rate/EMI constraints, and any external cabling.)

Group C – GPIO [17…20] (auto-direction translating buffer, 4 channels)

• This group has a datasheet maximum data rate of:
  • 24 Mbps for push-pull, and
  • 2 Mbps for open-drain.
• For a “clock-like” square wave, 24 Mbps corresponds to roughly ~24 MHz order-of-magnitude (and ~2 MHz for open-drain), depending on waveform/thresholds.

How to know if your signal is push-pull or open-drain (important for Group C):

• Push-pull: your driving device actively drives BOTH HIGH and LOW (typical CMOS/FPGA GPIO output). No external pull-up is required for logic-high.
• Open-drain: your driver only actively pulls LOW; logic-high is achieved via a pull-up resistor (typical I²C-style or “open collector/drain” outputs).
  If your interface uses a pull-up resistor to create logic-high (or the output type is described as open-drain/open-collector), treat it as open-drain and use the 2 Mbps guideline for Group C.

Group D – GPIO [21…24] (direct FPGA 3.3 V LVCMOS bank)

• These are direct 3.3 V LVCMOS FPGA GPIOs.
• Microchip indicates the FPGA GPIO can support up to ~1066 Mbps using single-ended standards in the GPIO banks.
• As a practical planning number for simple LVCMOS “GPIO-style” toggling on a board connector (not a tuned high-speed interface), it is reasonable to assume low-hundreds of MHz capability when lightly loaded, and tens of MHz when you have heavier loads or longer wiring. (If you tell us the load/cable length and whether it is clock-like or data-like, we can recommend which group to use with margin.)