Thank you for the answer.
You understood well, my idea had to do with whdload gaming.
Nevertheless is annoying that I cannot make the ACA500 to give me all 2 MB free.
I have turned everything off except the activation of the memory on board aca500 and booting from the A500 onboard rom 1.3, only the 1536 KB are visible. (booting workbecnh 1.3)
It does not seem to have a "hardware" problem this part of the memory since when I boot with maprom enabled, in Workbench 3.1 still have free the 1536 KB and I can play with whdload.
Anyone a possible solution?