ok, i solved the problem buying another xbox for few euros, it works so i installed the aladdin chips and when i turn on the xbox, there is no way to turn on the chip.
I get no FRAG, black screen or something else, the xbox just boot normally the microsoft dash. I've checked all the solder and they are ok.
The only strange thing i saw is the eject LED: when i press quickly the power button the led at the beginning is red, then became green (and the ms dashboard loads perfectly), and when i press the button for 1 second at the beginning the led is red, then came orange. If i'am not wrong, this is normal, but the fact is that as soon as i leave the button after 1 second the led became green booting the ms dashbard without problem.
I really don't understand, the LPC solder is ok because if they weren't the xbox had to FRAG...
Any of you had experienced a situation like that? Could be a problem of the chip (may be it fried with the old xbox)? I had thought also to an incompatibility between the xbox (a 1.4) and the chips (or better, the old bios)...can somebody help me? Thanks..