If the program is split into threads then these can run on a separate cores. Some Intel cups are a bit more complex and have something called hyperthreading which can be regarded as a virtual core.
So when I run TS2010 CM3 which is really multithreaded I'm seeing it use 8 cores on my four core Intel cpu.
In Driver mode TS2010 currently can only make use of two cores. However the operating system can sit on a different core.
One limiting factor on CPUs is normally heat so typically four cores are run slightly slower than two cores.
Then you have the problem of getting things into the CPU and out again, main memory is typically much slower than the speed that the CPU can handle so we buffer the CPU with cache memory. Basically you copy a block of low cost main memory onto a much more expensive high speed memory then the CPU reads the program instructions one at a time from the high speed or cache memory. This is what the L1, L2, and L3 caches are all about.
>As an example a quad core listed with 4gb of cache, does this equal 1gb per core
4 Gigs of cache memory would cost more than the rest of the computer and not offer much performance gain. 4 MBs or 1,000th of 4 gigs is much more likely. The answer is it depends on the caching algorithm and my expectation is that the cache will be shared over the cores. I seem to recall typically the L3 cache is shared but the L1 and L2 are more intimately connected to a particular CPU. On the i7 for example it has 4 x 256 KB L2 caches and a single 8MB L3 cache. Typically an 8 MB cache will not give twice the performance of a 4 MB cache. It's more can I find the memory address I need in this 4 MB copy or in this 8 MB copy of memory. Programs often run linearly so the next bit of memory required is often the adjacent memory location.
I run the slowest (cheapest) of the quad core Intel CPUs and I'm happy with the performance.
www.tomshardware.com/reviews/gaming-cpu-overclock,2772.html will give you a better idea or comparison.
Things to look for are thermal envelope you want this to be lower rather than higher. Process 45 mm is good, smaller is better. You're probably going to be running the PC for a number of years by which time Trainz may well be running on more cores in Driver. However many motherboards will accept both dual and quad cpus so buy a dual today and do a mid life upgrade with quad core is a quite reasonable approach.
Cheerio John
