The Axon does not actually output the graphics engine on the SDI card. The output on the SDI card will only mirror whatever you are sending to the SDI input, and it will do it at the same format as the input. In other words, if you are inputting an NTSC signal, it will output NTSC.
When Axon first began shipping, it had a standard definition SDI card. Starting with serial numbers 76CGxxxxxxx, it began shipping with the HD SDI card.