It sounds like you're encountering a compatibility issue with the new 5800x and your X570 Tomahawk motherboard when trying to enable Smart Access Memory. Some possible causes for this issue could be outdated or incorrect BIOS version, incorrect driver version or incorrect memory configuration.
Here are a few steps you could try to resolve the issue:
Make sure you're using the latest BIOS version for your X570 Tomahawk motherboard.
Check the AMD website for recommended memory configurations for the Ryzen 5800X and make sure your memory modules match the recommended configuration.
Check that you have installed the latest chipset and GPU drivers for your system.
Try clearing the CMOS (by removing the battery or using the clear CMOS jumper on the motherboard) and then reconfiguring your memory and other settings in the BIOS.
If none of these steps help, you may need to reach out to the support team for your motherboard or the manufacturer of your memory modules for further assistance.