SQL Server can't see 80 CPU

I have a server with 4*20 CPU.  Windows 2008 R2 Ent., SP1.  The OS sees 80 CPU (16*5)  in TSK MGR.   SQL Server 2008 SP3 CU9  only sees 40 .....

using the following query: 

SELECT cpu_count AS [Logical CPU Count]
, hyperthread_ratio AS [Hyperthread Ratio]
,cpu_count/hyperthread_ratio AS [Physical CPU Count]
, physical_memory_in_bytes/1048576 AS [Physical Memory (MB)]
, sqlserver_start_time
FROM sys.dm_os_sys_info OPTION (RECOMPILE);

Why ?

sgb