user: Question: How many shader models have a 900 core clock ( mhz )?
Columns: ['Graphics', 'Launch', 'Market', 'CPU', 'Code name', 'Device ID', 'Core clock ( MHz )', 'Execution units', 'Shader model', 'DirectX', 'OpenGL', 'OpenCL', 'Memory bandwidth ( GB/s )', 'DVMT ( MB )', 'CVT HD', 'QSV']
Types: ['text', 'real', 'text', 'text', 'text', 'real', 'text', 'real', 'text', 'text', 'text', 'text', 'text', 'real', 'text', 'text']
Sample row: ['HD Graphics', 2010.0, 'Desktop', 'Celeron G1101 PentiumG69xx', 'Ironlake ( Clarkdale )', 42.0, '533', 12.0, '4.0', '10.0', '2.1', 'No', '17', 1720.0, 'No', 'No']
SQL:

assistant: SELECT COUNT("Shader model") FROM "Table" WHERE "Core clock ( MHz )" = '900';