Why is my Celeron core duo WinXP laptop running code faster than a 64-bit Win7 multicore workstation?

I have an ageing laptop running 32-bit XP with an Intel Core Duo Centrino CPU and 2GB of RAM. I also have a two year old workstation with dual Xeon quad-core 2.4GHz processors and 48GB of RAM. I have 32-bit Matlab 2012b installed on the laptop and 64-bit Matlab 2012b on the workstation. When running 'bench' as you would expect the workstation is over twice as fast on the computation tasks as the laptop. However I've noticed that when running some optimisation code I've written, using identical datasets and control parameters, the laptop is significantly faster than the workstation (157s elapsed time vs 208s elapsed time). This struck me as odd - can anybody suggest any reasons why?

[per isakson]

Did you try to run profile?

Answer 1

[Robert Low]

Per, I have run the profiler on both machines but as it is the same code (with the same input values) the distribution of CPU time seems pretty similar in both reports. The puzzle is why the nominally faster machine is actually running more slowly.

I can't post the code here as it contains confidential algorithms.