Psuedorandom numbers

[Los Frijoles]

Well I have been studying psuedorandom sequences for Microchip microcontrollers based on seeds and so far the fastest I have found is thusly from mondo technology:

chop    movf    val1,w     ;get the 1st
        addwf   val2,w     ;add the 2nd
        movwf   val2       ;store the 2nd
        addwf   val3,w     ;add the 3rd & store
        movwf   val3       ;back in 3rd
        addwf   val1       ;add back to 1st
        swapf   val1       ;swap nibbles
        movf    val1,w     ;return one byte
        ret

It looks to be 10 instruction cycles long. However, I would like to see some other methods as I have found that this particular algorithm tends to repeat numbers after a short while with only a 24-bit seed. Does anyone else know of some psuedorandom sequences (C, ASM, or Psuedocode please)?