using System;

using System.Collections.Generic;

using System.Linq;

public class Program

{

    public static void Main()

    {

        var prefixes = new List<string>() { "INTEL", "AMD", "IN" };

        var parameterValues = new List<string>() 

        {

            "INTEL I7", "INTEL I5", "INBLALBA", "AMD5", "INTEL I3", "AMD3", "BLABLA", "BLABLA2", "intel pentium"

        };

        var q = from pv in parameterValues

                    let foundPrefix = prefixes.FirstOrDefault(p => pv.StartsWith(p, StringComparison.OrdinalIgnoreCase))

                    select new { pv, foundPrefix };

            var result = q.GroupBy(a => a.foundPrefix).ToList();

            var final = result.ToDictionary(g => g.Key ?? "others", g => g.Select(a => a.pv).ToList());

            Console.WriteLine(final.Aggregate("", (acc, kvp) => string.Format("{0}\n{1,10}: {2}", acc, kvp.Key, string.Join(", ", kvp.Value))));

    }

}