Yes, that was pretty clear, but in the D version that's not enough to make it compile, there is also the missing functionID which apparently needs to be primed with the correct value to make things work. No idea what that value should be though.
It's not that I thought that this information was difficult to look up, rather it seemed very odd information to be missing from a link that was submitted as useful/interesting.
functionID is what's called "standard level" in the link I posted. So it should be 4 (you can also see that in the C version btw.).
I agree that the example isn't very well tested - the author probably pulled it out of some existing code and wasn't very careful.
Basically on x86 CPUs you can use the cpuid instruction to get information about the CPU and the cache: http://www.sandpile.org/x86/cpuid.htm
The code in the first snippet uses a compiler intrinsic to execute this instruction and calculates the cache size from the result. In the second snippet the assembler code is written by hand instead.