Nearly identical code with different running time Why?

I'm testing two nearly identical codes with a tiny difference on one of the for loops. The first uses three loops to iterate indexes y,z,x while the second iterated x,z,y.

My question is why the difference in user time and wall clock time? Is it because of the memory locations in one code and the other?

test_1.c:

#define N 1000

// Matrix definition
long long int A[N][N],B[N][N],R[N][N];

int main()
{
    int x,y,z;
    char str[100];

/*Matrix initialization*/ 
    for(y=0;y<N;y++) 
        for(x=0;x<N;x++)
        {
            A[y][x]=x;
            B[y][x]=y;
            R[y][x]=0;
        }
/*Matrix multiplication*/
    for(y=0;y<N;y++)
        for(z=0;z<N;z++) 
            for(x=0;x<N;x++) 
            {
                R[y][x]+= A[y][z] * B[z][x];
            }   
exit(0);
}

The difference in the second code (test_2.c) its on the last for loop:

for(x=0;x<N;x++)
    for(z=0;z<N;z++) 
        for(y=0;y<N;y++) 
        {
            R[y][x]+= A[y][z] * B[z][x];
        } 

If I print /user/bin/time -v ./test_1 I get the following stats:

Command being timed: "./test_1"
User time (seconds): 5.19
System time (seconds): 0.01
Percent of CPU this job got: 99%
Elapsed (wall clock) time (h:mm:ss or m:ss): 0:05.22

While /user/bin/time -v ./test_2 gives the following stats:

Command being timed: "./test_2"
User time (seconds): 7.75
System time (seconds): 0.00
Percent of CPU this job got: 99%
Elapsed (wall clock) time (h:mm:ss or m:ss): 0:07.76