Comparing the two IMs raises all kinds of interesting and subtle issues.

The 605 has no documented "laptop" config (although obviously it must contain a microprocessor etc). The 605A has extensive config, and is obviously a PC board (even has a USB port, although it is undocumented).

Other subtle things are e.g. why P2 (the big 78 way connector) has been provided when in most installations all the required signals are duplicated on the old P1 (25 way). In an upgrade situation it would be silly to rewire the P1 plug to the P2 plug (which is probably a really pricey Positronic job, with $1 each for the crimp pins, FWIW :) ).

Another curious one is that the micro appears to be scanning all the RS232 ports for the string "command" on a continuous basis, and when it sees this, that port becomes the config port. This is fine but (I am an embedded system hardware/software dev, industrial electronics) is really quite unusual! They sort of try to steer you to using P4 though.

I currently have a 605, installed in 2012. The upgrade is avionics shop performed but they are just wiremen really.

Another Q is more complicated, and may be nonsense in the USA context: does anyone here have direct experience with whether a 605A shows targets with SIL=0 on your display device and what is that display device? I am pretty sure (from Support) the 605A will pick these up but some display devices (probably Garmin, fed via RS232) will strip them out. ARINC429-fed displays cannot strip them out because the packets don't carry that info. SIL=0 is "uncertified" ADS-B OUT but is widely used in Europe; there is a ton of oddball boxes, Raspberry PI based, which people fly with, with their Mode C/S transponder firmly turned off :)

Thank you for any info.