We made an official house rule that it's 1 sensor point/1 port, which makes sense in the context of how it works with cybernetic/natural/external tech senses in M&M. I treat the sensors as external senses, which under the description in M&M leads to the above result. I guess you could narrow it down even further to specific sensors using the descriptions in SR3, but 1 sensor rating point: 1 port is just easier, especially when the Sensor rating gets to the upper limits where it's not so much new sensors as
better sensors.
Overload is when Essence hits 0 because they have so many generic or dedicated ports combined with all of their other cyber. The whole point of the tactical computer is that it does all of the heavy lifting of data processing and tactical analysis for you. This is why it's such a great piece of tech - it makes a user with a lot of senses very dangerous.
Using the Sensor rating/port example, you'd need a dedicated port with hardwired tactical software for each point of Sensor, or tactical programs in headware memory if you are using generic ports. If it's straight Sensor:Port (e.g., count proximity sensors, rangefinders, video, radar, signature-recognition, low-light and telescopic enhancements as individual "senses" instead of lumping them together as they are all included in Rating 1 Sensors) then you need the tactical software for each sense. So a vehicle with just Rating 1 Sensors would require 7 dedicated ports or 7 generic ports and 7 tactical programs for each "sense." So with a Rating 1 Sensor vehicle, your Rigger is now running around with a Level 3 Tactical Computer (This is why I treat each Sensor Rating as 1 "sense"). Add GPS (kind of a "duh" addition if you ask me) and he now has a Level 4 Tactical Computer and all that entails (and it entails a lot for Vehicle Combat) including an effective Skill of 4 in Small Unit Tactics (Vehicle).
Oh, as for Drone? To count as a "sense" for the Tactical Computer (and therefore, even higher bonus for drone warriors), each of the drones has to have
at least 1 port for their sensors. But then you can hook the tactical computer into your BattleTac IVIS system, and your drones will be unstoppable when you get the Tactical Computer bonus for making the IVIS Small Unit Tactics (Vehicle) test to jack up the Comprehension and IVIS Pools. It also would be required to use the Tactical Computer bonus when you're using FDDM. I also toyed with the Combat Pool bonus becoming a Control Pool bonus when rigging.
Oh, and in case you're wondering: I allow the Tactical Computer to be used in the Matrix. It works quite well in conjunction with the BattleTac Matrixlink software. In that event, each "sense" to be ported is a 1:1 with your deck's (and teammates/frames, if applicable) Sensor Rating(s). So if you have Sensors 6, and 6 dedicated or generic (with the applicable tactical programs) ports, you now possess a Level 3 Tactical Computer to use in cybercombat (e.g., Small Unit Tactics (Matrix) skill is + 3, and so on) - reflected ruleswise by adding the CP eqv. bonus to Hacking Pool
for cybercombat only.
BTW, in case you're wondering - I've seen Tactical Computers installed in Blues and linked to Deus. The resulting Combat Pools were in the high teens, and they were virtually impossible to surprise (they easily had Level 4 Tactical Computers, which gives you access to 100% of CP when making Surprise Tests). Tactical Computers, Snake-Eyes FDDM, and Deus are an almost unstoppable combination. There really is no better reason I have seen as to why Tactical Computers should keep their high Availability and Street Index ratings as when I look at the stats for Tadashi Marushige in Brainscan after he is given a Tactical Computer (and why the hell didn't he have one in the first place anyway?).
Drone Networks and Tactical Computers