Ah, it seems I am able to bring up the menu 100 % reliably on the M4A78-EM as well by hitting and holding the shift *immediately after firmware initialization screens* (Asus’ boot graphic and ATA Security eXtension). So holding shift from power-up or from the boot graphic screen won’t work in this setup, but seems to work with others (such as my FS laptop). I’d expect it to work from power-up consistently across different setups.