| Operating Systems | Service Pack
 | Max. Physical
 Processors
 Supported
 by OS
 | Processors Detected
 by OS on
 Altos R920
 | Note | 
| Windows Server 2003 R2 Standard Edition
 | SP2 | 4 | 16 | 1,2 | 
| Windows Server 2003 R2 Enterprise Edition
 | SP2 | 8 | 16 | 1,2 | 
| Windows Server 2003 R2 Standard x64 Edition
 | SP2 | 4 | 16 | 1,2 | 
| Windows Server 2003 R2 Enterprise x64 Edition
 | SP2 | 8 | 16 | 1,2 | 
| Red Hat Enterprise Linux 5 x86 | N/A | 32 | 16 |  | 
| Red Hat Enterprise Linux 5 EM64T | N/A | 64 | 16 |  | 
| SuSE Linux Enterprise Server 10 x86
 | SP1 | 32 | 16 |  | 
| SuSE Linux Enterprise Server 10 EM64T
 | SP1 | 128 | 16 |  | 
| NOTE 1. Both Standard and Enterprise Edition of Windows Server 2003 can support 16 logical processorson Altos R920. 
 NOTE 2. Windows Server 2003 license is based on physical processor. (One quad-core processor onlyrequires one processor license). Please refer to Microsoft for more detail.http://www.microsoft.com/licensing/highlights/multicore.mspx
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