I would like to know what made your multi a 23, and a 27, perhaps run something like pi with 200 bclk and default multi. Then run with your 27 multi and see if performance is similar, or the higher multi shows a significant increase. 200 no work try something that the 27 multi can handle. If simular then it is just a glitch if significant difference well you may have something there like a freak CPU.