You need to enable the ATX power switch functionality, and save that as the 633's default boot state. From the
633's data sheet:
28: Set ATX Power Switch Functionality
This command allows the 633 to replace power and reset switches in an “ATX” compatible system.
The ATX Power Switch Functionality is one of the items stored by the “4: Store Current State As Boot State” command. (So use that command if you want the 633 to continue working as the power switch 
)
There are four functions that can be enabled by this command:
KEYPAD_RESET: If POWER-ON SENSE (GPIO[1]) is high, holding the green check key for 4 seconds will pulse RESET (GPIO[3]) pin low for 1 second. During the 1-second pulse, the 633 will show “RESET”, and then the 633 will reset itself, showing its boot state as if it had just powered on. Once the pulse has finished, the 633 will not respond to any commands until after it has reset the host and itself
KEYPAD_POWER_ON: If POWER-ON SENSE (GPIO[1]) is low, pressing the green check key for 0.25 seconds will pulse POWER CONTROL (GPIO[2]) low for 1 second. During the 1-second pulse, the 633 will show “POWER ON”, then the 633 will reset itself.
KEYPAD_POWER_OFF: If POWER-ON SENSE (GPIO[1]) is high, holding the red “X” key for 4 seconds will pulse POWER CONTROL (GPIO[2]) low for 1 second. During the 1-second pulse, the 633 will show “POWER OFF”. In order for the system to look “off”, the 633 will then clear its screen. The fans will stop and the backlight will go off if the host drops the +12v supply, which would be expected. The 633 will then “sleep”, waiting for POWER-ON SENSE (GPIO[1]) to go high or a packet to be received.
LCD_OFF_IF_HOST_IS_OFF: If you have set “LCD_OFF_IF_HOST_IS_OFF” The 633 will then blank its screen to simulate its power being off any time POWER-ON SENSE (GPIO[1]) is low. The 633 will still be active (since it is powered by VSB), monitoring the keypad for a power-on keystroke and monitoring its serial connection for a packet from the host. If +12v remains active (which would not be expected, since the host is “off”), the fans and backlight will remain on at their previous settings. Once POWER-ON SENSE (GPIO[1]) goes high, the 633 will “un-blank” its display.
Code:
#define LCD_OFF_IF_HOST_IS_OFF 0x10
#define KEYPAD_RESET 0x20
#define KEYPAD_POWER_ON 0x40
#define KEYPAD_POWER_OFF 0x80
type = 28
data_length = 1
data[0]: bit mask of enabled functions
So use the following sequence of commands in
633_WinTest's "packet debugger" window:
Code:
{set command to}28: Set ATX Power Switch Functionality
{set data to}/224
{click "send packet"}
{set command to}4: Store Current State As Boot State
{no data}
{click "send packet"}
Whatever is displayed when you do the "4: Store Current State As Boot State" will become the boot screen (as well as contrast, backlight, fans, and special characters).
