There is no one function or procedure to get extended information on the CPU. Intel supplies a CPUInfo Package that you can download and use in your application. However, the sample code is in C, and I took the liberty of creating a sample Delphi application using the package. Note: the Intel package was only designed for Intel's processors, and this sample project is designed to work on most processors (AMD, Alpha, MIPS, etc.).
Note: this project is rather old and you can get other newer libraries for CPU detection such as CarbonSoft cxCPU or MiTeC System Information Component.
Download my sample Delphi application CPUTest (~16KB). Tested OK in Delphi 3, 4 & 5.