Yeah, itīs distictly possible that weīre just not getting what you mean to say.
I canīt say much, as I only really know 2 languages, bad English, and extremely bad English. Not counting a few words here and there in a sentence spoken in German or Spanish. But I can curse in both rather well if that counts.
No problem, hope you get it sorted soon from them.
Wayne's got it...
Even VGA cable has a gnd, but you pulled that cable.
The only thing you had was M4 to PC - both power(s) and ground - otherwise it wouldn't work.
But let's say you disconnected the M4 to PC ground but left the VGA connected (in turn being powered from the M4 or M4's battery or supply) - then the PC could remain powered using the VGA ground.
But a VGA ground is a signal ground (whether it's a reference voltage or a shield) and NOT a power ground - hence might not handle the PC's current. Hence smoke, fuse, burn etc.
As I think you now know - there must be a "ground" (and power) if it/anything is to work.
It may be a poor ground, hence not fully operational, but for any response, power-flow is needed.
Hence the electricity must be able to flow in a complete loop - from the power source through the load & back to & through the power source. (Like hydro-electricity - the water/rain has to get to the dam etc, then through & evaporate again... It's a true solar-power system.)
Sometimes the loop can include air - ie arcs & sparks (like splugs, aka spark plugs), but that is rare in 12V systems...
As to noise.... oh poopy-doo - how many GB storage do we have?
All electrical devices cause noise. Many are noisy - especially modern "SMPS" (switching) power supplies & converters. But that noise is usually suppressed by the manufacturer etc.
The M4 however is a very noisy device. That's what Mickz's thread ascertains.
A detailed solution is a shielded enclosure (to stop noise radiating out) and filters on input/output leads (special caps, or inductors, toroids, ferrites etc). But that's to minimise radio interference (AM, FM, GPS etc) - it may not have to be that robust to prevent interference to PCs etc.
But even with perfectly quite electronics, noise can occur in 2 common ways.
1. Poor grounds - shielding and filtering usually involves shorting or dumping or passing the interference to ground. The poorer the ground, the more noise that remains in the systems.
2. Ground Loops. While these happen in domestic (house) systems due to stray AC fields and "induction loops" (usually), they also occur in DC systems due to IR losses (i*R = current x resistance) which is another way of saying voltage drop. (From Ohms Law: V = IR.)
Because power to a device means current through a cable with some resistance, there is therefore a voltage drop along that cable. That includes the ground path.
This in turn can cause noise.
The problem is that whereas classical ground loops can often be overcome by grounding at a single point, that may not work in all cases.
DC systems are worse because unlike AC systems, they are usually not "floating". (In an AC system, after voltage conversion, one side of the output is or may be connected to the input ground - meaning "safety ground" or ground/earth stake.)
And in cars, signal grounds and power grounds are often the same.
Otherwise, digital circuits (for example) almost always have separate digital and analog grounds which are probably separate from power (or heavy current) grounds... Although they will be interconnected, that is usually done at one point only - ie the "single grounding point" principle.
Not that the latter is any solution - it's just pointing out the "other source" of noise (if not using and M4 LOL!).
i admit, i did not read every post, but unles i missed it, i think there is some details missing:
you say that the computer will stay running without the ground wire from the m4 in place. i believer that this is part of your problem-- as wayne, and oldspark touched on, there is somewhere else that the system is getting grounded-- the other ground is probably also what is causing the noise(a ground loop is when there is a voltage difference between ground points-- typically causing the problem you describe)
could you post a diagram of your entire setup, including where everything is grounded, and getting power from?
I'm guessing if you unbolt the motherboard from the case it won't run with the ground disconnected. If you have everything else disconnected then the only thing it could be grounding on is the case - If you think of your cars ground the only thing it grounds to is the body (well, and engine, but thats just another lump of metal), it doesn't actually run to ground (the earth). Just as an aside - theres no actual "ground" its just a reference - not ZERO volts, its just the positive is 12 volts ABOVE whatever the ground is.
I just noticed the complete repeat of my reply for a simple SSD statement...
Do motherboards really depend on case grounding for their ground?
That is BAD design! It belongs back in the days of single-line power (single-line telegraghs and AC distribution).
Zero volts is always a reference unless talking about a potential difference (no pun).
We call "ground" and "earth" or - in vehicles etc - sometimes a chassis.
It simply means the common reference - like sea level - though it also confers shielding etc in electrical situations (like a Faraday cage).
Don't forget, the "ground" in a vehicle is the battery or the alternator. They are then interconnected via the body/chassis/engine metalwork - aka ground/earth/chassis/zero. (I won't get into semantics of "absolute ground" - I fail to see its significance. And most seem not to recognise it changes from battery to alternator LOL!)
Ah yeah - schoolboy error there sorry. I was trying to think of an analogy where the power in the motherboard could find its way to the case.
And suspected, hence my wording. (If... then... bad..)
But it touches on the old multi-point "zero" volts (grounding) or single point grounding.
(Of course - separate digital and analog (and power) grounds with single interconnect point...)
But it's hard to provide a slid grounding on that subject.... [ha ha lol... pun... But even I didn't believe in "ground loops" in cages cars until recently - though that is partly a "definition" issue, and extreme situations (ie, stupid 12V distribution for high power systems!).]