Bored of reverse engineering, I decided to muck about with the extra instructions intel added. Unfortunatly I get an illegal instruction, when executing this:

#include <stdio.h>

unsigned int getAccLo ( void )
    unsigned int accHi;
    unsigned int accLo;
 "MRA %0, %1, acc0"
    return accLo;

int main (int argc, char *argv[])
    printf("lo : %d \n", getAccLo());
    return 1;

Probably needs the kernel to enable something. Downloading the pxa255 datasheets...