This is exactly correct. In Windows a swap file is on the hard disk which is exceedingly slow compared to main RAM. On the GP2X, if you used the SD card it'd be far slower than RAM, especially with the lack of DMA, but it might be pretty snappy with NAND-- that is, to read from. You would want to write to NAND at a time when there is not much going on, because it's going to take a little while compared to reading it.