I somehow succeeded to enable all of 256MB SDRAM at 133MHz, and to enable video using ADLO with original VGA BIOS, on EPIA 5000.
cool.
It now boots into GRUB in less than 2 seconds. :) (It's too fast for IDE drive to spin up, so I have to hit reset button after cold start.)
hmm, in rombios.c, can you try increasing ATA_WAIT_COUNT by magnitude or two and see if it helps?