I have recently booted my ailing EX485 with and external USB BartPE hard drive for diagnosing purposes. I used a KVM PS/2 connector which I bought from cakalapati aka Charles see the following link,
viewtopic.php?f=6&t=14074The KVM I bought worked like a charm with the jumper on JP2 (I think). I was able to use a VGA connector and a USB mouse and keyboard. Had the external drive on the lowest rear USB port the keyboard above that and out of habit the USB mouse on the front USB port. I am hoping to boot with Windows 8 TOGO in the next few days. The I am dealing with now is bubbled capacitors in the PSU. A new PSU is on order.
Hope this helps.