According to the HP ENVY m6 Sleekbook HP ENVY Touchsmart m6 SleekBook HP ENVY TouchSmart m6 Ultrabook - Maintenance and Service Guide, this model should support the following CPUs;
Intel® Core™ i7-4500U (1.8 GHz, turbo up to 3.0 GHz) 1600 MHz/4MB Cache, Dual 15W
Intel Core i5-4200U (1.6 GHz, turbo up to 2.6 GHz) 1600 MHz/3MB Cache, Dual 15W
Intel Core i3-4010U (1.7 GHz), 1600 MHz/3 MB L3, Dual 15W
however, the MSG doesn't list an HP p/n for these CPUs and the system boards all state "for use in computer models equipped with Intel i5-4200U processor" as follows;
732775-001 System board for use with computer models equipped with Intel i5-4200U processor and a non-
Windows 8 operating system
732775-501 System board for use with computer models equipped with Intel i5-4200U processor and the Windows
8 Standard operating system
732775-601 System board for use with computer models equipped with Intel i5-4200U processor and the Windows
8 Professional operating system
745043-001 System board for use only with computer models equipped with Intel Core i5-4200U processor and a
non-Windows 8 operating system (with upgraded CPU core power controller version)
745043-501 System board for use only with computer models equipped with Intel Core i5-4200U processor
If you have any further questions, please don't hesitate to ask.
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