You can find a list of SAP-certified Dell hardware:

PowerEdge R900 Dell PowerEdge R900
The Dell™ PowerEdge™ R900 server is a four-processor, Intel-based rack server.
For more information, visit the Dell site.
certified for: Linux
PowerEdge 6950 Dell PowerEdge 6950
The PowerEdge 6950 is a four-processor, AMD-based rack server.
For more information, visit the Dell site.
certified for: Windows and Linux
PowerEdge 2970 Dell PowerEdge 2970
The PowerEdge 2970 is a two-processor, AMD-based rack server.
For more information, visit the Dell site.
certified for: Windows and Linux
PowerEdge 1955 Dell PowerEdge 1955
The PowerEdge 1955 is a two-processor, Intel-based blade server.
For more information, visit the Dell site.
certified for: Windows and Linux
PowerEdge 1950 Dell PowerEdge 1950
also called: PowerEdge 1950 III
The PowerEdge 1950 is a two-processor, Intel-based rack server.
For more information: visit the Dell site.
certified for: Windows and Linux
PowerEdge 2900 Dell PowerEdge 2900
also called: PowerEdge 2900 III
The PowerEdge 2900 is a two-processor, Intel-based tower server.
For more information, visit the Dell site.
certified for: Windows and Linux
PowerEdge 2950 Dell PowerEdge 2950
also called: PowerEdge 2950 III
The PowerEdge 2950 is a two-processor, Intel-based rack server.
For more information, visit the Dell site.
certified for: Windows and Linux
PowerEdge 6800 Dell PowerEdge 6800
The PowerEdge 6800 is a four-processor, Intel-based tower server.
For more information, visit the Dell site.
certified for: Windows and Linux
PowerEdge 6850 Dell PowerEdge 6850
The PowerEdge 6850 is a four-processor, Intel-based rack server.
For more information, visit the Dell site.
certified for: Windows and Linux