Basic Instance Info - DMOs

SELECT cpu_count AS logical_cpu_count,
               cpu_count / hyperthread_ratio AS physical_cpu_count
               CAST(physical_memory_kb / 1024. AS int) AS physical_memory_mb,
               sqlserver_start_time
FROM sys.dm_os_sys_info;

The last column 'sqlserver_start_time' tells you whether it makes sense to further analyze cumulative information or not.