This query actually tells you the CPU utilization by SQL Server 2008, in one minute increments.

-- Get CPU Utilization History for last 30 minutes (SQL 2008)

DECLARE @ts_now bigint = (SELECT cpu_ticks/(cpu_ticks/ms_ticks)FROM sys.dm_os_sys_info);

SELECT TOP(30) SQLProcessUtilization AS [SQL Server Process CPU Utilization],

SystemIdle AS [System Idle Process],

100 - SystemIdle - SQLProcessUtilization AS [Other Process CPU Utilization],

DATEADD(ms, -1 * (@ts_now - [timestamp]), GETDATE()) AS [Event Time]

FROM (

SELECT record.value('(./Record/@id)[1]', 'int') AS record_id,

record.value('(./Record/SchedulerMonitorEvent/SystemHealth/SystemIdle)[1]', 'int')

AS [SystemIdle],

record.value('(./Record/SchedulerMonitorEvent/SystemHealth/ProcessUtilization)[1]',

'int')

AS [SQLProcessUtilization], [timestamp]

FROM (

SELECT [timestamp], CONVERT(xml, record) AS [record]

FROM sys.dm_os_ring_buffers

WHERE ring_buffer_type = N'RING_BUFFER_SCHEDULER_MONITOR'

AND record LIKE '%<SystemHealth>%') AS x

) AS y

ORDER BY record_id DESC;