I have an x220 with a 2.6GHz i5-2540M CPU and 16GB of DDR3 1866 Crucial Ballistix Sport RAM. The BIOS is a modified version of 1.40 with adjustable RAM speeds. Ran a couple quick benchmarks using PC Benchmark
from Jujuba Software.
Memory set to 1333MHz gave these results:
- GPU Compute: 162.01 speed ops
- Main RAM: 1,875.20 MB/s
Memory set to 1866MHz gave these results:
- GPU Compute: 174.98 speed ops
- Main RAM: 2,329.60 MB/s
Pretty decent improvement in memory speed and some modest gains in GPU performance. Can't say I really notice any difference with day-to-day use, though.
Edit: Ran some additional benchmarks with PerformanceTest 8.0 - red is 1333MHz, green is 1866MHz: