1) Ok. But will it be cheaper for end users buying desktop PCs? Remember that there might be additional costs pushed to the motherboard manufacturers (e.g. for having to keep more SKUs), and then onwards to the consumers.
Who knows. This is not necessarily on the radar of anyone who is making these decisions. Very likely it will cost consumers the same initially, with any savings passed on as margin until price battles bring prices down to earth.
For an example of this see AMD Brazos platform. These were supposedly VERY cheap setups, but initial prices rivaled low end celeron + mobo prices... fast forward 9 months and the pricing was VERY different.
I don't expect BGA to do much to prices until at least a year after introduction. The landscape has changed. Companies used to price their way to volume. I think the market is less elastic than it's ever been and combined with less competition, the "race to the bottom" is very slow.
2)
a) Well, the I/O connector block only has to be around 10-15x3x3 cm. And since Mini-ITX motherboards are 17x17xHeight cm there should be room for size reduction, right? After all, moving the VRM and PCH off the motherboard should enable smaller motherboards.
b) What components will actually be left on the motherboard if the VRM and PCH is integrated in the CPU?
You still likely need inductors off CPU... I suppose it depends on total capacity, but CPUs aren't all that need power regulated by the motherboard. It depends on the method of implementation how the VRM integration works out.
PCH integration will free up the chip itself, but you still need traces and such. The rest is all power connectors, memory slots, SATA ports, etc... I don't see the form factor getting any smaller without significant re-design of some standard connector interfaces (SATA, PCI-E, USB, Network, etc...)
I think you'll see the extra space used by adding some SATA ports or USB to current designs. It's not going to be a smooth transition to anything smaller than the standard I/O interface and 1 PCI-e slot that mini-ITX is now. Memory interface takes up lots of space, ATX connector + 4 pin takes up a lot of space, etc...
Eventually a smaller form factor will be released, but I think it will take a lot more than integration of the PCH & VRM. It requires a whole new set of standards on connectors. Standards that I don't think are likely to materialize given reduced consumer volume on building PCs from parts... It's a shrinking market and I don't think it will be catered to in the same way it has in the past. OEMs can build whatever custom setups they want, and I think you'll see that continue. Smaller than ITX form factor as a standard is going to give up a lot of flexibility... which further shrinks the pool of potential customers. Time will tell, but I'm not optimistic that it'll happen.
3. True. But with 14 nm comes lower TDP. And moving the VRM and PCH on die will also lower TDP. So it's not really an effect of going BGA only...
That was my point. BGA doesn't do anything like that, but history is that things are moving towards fitting more powerful computers into smaller form factors through improved processes and reduced thermals. That's just what happens, so yes, the future will put something the power of a 3570k into a fanless form factor... eventually.
Fanless means about 10-15 watts (for the entire system) or a VERY expensive case. These are tablet power envelopes... So the question is whether or not you'll even care by the time something like that is available... because there'll be something that will run in mini ITX with a VERY quiet fan at 50 watts that will be MANY times faster... and it some cases cheaper or the same cost. Most people will opt for the more powerful option that has a fan that's inaudible at normal seating postion,
It really depends on the software and what CPU that requires by then. I mean if you compare current fanless options, they are probably about as powerful as top of the line 6 years ago athlon x2s... but the industry has moved beyond these being a minimum, so nobody really cares about those options except people who only do stuff that a tablet is sufficient for. Where the software is at the time will dictate whether people will care. I doubt gaming CPU requirements will remain that stangnant, but it's possible. Other types of consumer level programs will probably remain reasonably stagnant, but most of these need well under i5-3570 level performance.
4. Yeah, probably correct. Is that the main driving force for Intel going BGA only? And if so, why didn't it happen earlier, before Broadwell?
When you're as big as Intel, you take as small a step as you NEED to. ATOM development took baby steps for years... and left the door open for ARM. Now ATOM is taking huge catch-up strides. The best operation mode is metered but continuous improvement. small steps mean less risk. But competition forces bigger risks.
You can also look at the chipset design as another example. 65nm for generation after generation after generation. Why are they moving now? Tablets are forcing their hand.
Why are they pushing integration harder now then ever? Tablets and to a lesser extent smartphones.