using System;
using System.Linq;
using System.Text.RegularExpressions;
public class Test
{
	public static void Main()
	{
		var re = @"GeForce\s+\w+-([^\W\d]*(\d+)[^\W\d]*)-([^\W\d]*(\d+)[^\W\d]*)"; 
		var str = "GeForce TURBO-GTX1080-8G NVIDIA\nGeForce TURBO-GTX1070-4Gi"; 
		var res = Regex.Matches(str, re)
				.Cast<Match>()
				.Select(m => new[] {m.Groups[1].Value, m.Groups[2].Value, m.Groups[3].Value, m.Groups[4].Value} )
				.ToList();
		foreach (var m in res)
			Console.WriteLine(string.Join(" : ", m));
 
 
	}
}

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