Well not exactly
Correct me if I'm wrong, alright?
The current iMac uses an Intel logic board (What I'm calling a chipset, is that the wrong term?)
Unfortunately yes it is a bit confused. A chipset gets soldered to a motherboard with a lot of other stuff, so you are not exactly on the same page here. Generally a Intel chipset consisted of the processor, and the so called north and south bridges. The level of integration generally increased with each new revision of these chipsets. Not too this isn't the whole computer as a number of other things get connected to the chipsets including RAM and some form of ROM/Flash.
They are moving towards an Nvidia board.
That is they are going to a Nvidia chipset of some sort. That based on the info leaked in Apples latest software releases. Note that we don't know exactly what variant of the 9400M this might be. It could be the very same mobile chip used in the new MacBooks, it could be a variant clocked faster or it could be another member of the family with a different feature set.
The important thing to remember is that Nvidia has already acknowledged that what became the 9400M was initially suggested to Apple as a desk top chip. There is a good possibility that there is a faster 9400M type chip with a desktop interface in the wings.
Still building off the Mobile Montivia Platform.
Could be or it could be Intels current desktop chips. I'd love to see i7 but that would imply that Nvidia has a variant of 9400M ready to go with a quickpath interconnect.
My point is that the iMac does not require a mobile chip. If the computer is scheduled for a redesign they can throw anything they want into it. The only limitation being thermal management within Apples noise guidelines. Going desktop does however allow them to keep more current with processor specs.
While it probably doesn't mean much now, people have rightly pointed out iMacs lack of a quad core CPU. It would be far easier for Apple to keep the specs competitive if they used desktop chips. I mentioned now on purpose because for most uses dual core does pretty damn good with todays software and the demands of a general user. That may not be the case in the future so arguments about iMac trailing in CPU count may have more basis in reality.
i7 is a desktop chip. There isn't a Mobile Montivia platform that will accept the chip. (At least I'm not aware of any.)
Well not that we know of. You are assuming that a mobile platform is required though and that is what I'm having trouble with. It isn't and frankly the current iMacs are a bit of a hybrid design as it is. Apple can be very creative with respect to what they put into the iMac.
Further the finds about the iMacs coming GPU really don't indicate that that GPU is using a mobile bus interface. Just recently Nvidia announced a variant of the 9400M with a bus interface for ATOM. They could just as well have an interface for the desktop processors of today or even quickpath.
I also think you are putting a little too much faith in a non-SJ keynote at MWSF. I think Spec bump to 4-core Penryn chips and maybe a case design to look like the new ACD.
Well frankly I don't know what to think of the lack of SJ at MWSF. I don't believe it has anything to do with what comes out at MWSF, except for the possibility of a blockbuster device. Remember last years MWSF was kinda underwhelming as it was and Apple had weekly product releases for about two months after MWSF. They might not have anything of substance for the show but for me that is speculation right now. It really looks like dropping out of MWSF has been in the works for a couple of years now. I'm more worried that there haven't been any juicy leaks yet.
In any event I'd be the first to admit that i7 is a stretch. It would however be good to see Apple really stretching to innovate and bring bleeding edge products to the market. Further if they don't go i7 but do deliver a totally redesigned iMac, using the older mobile technology, that would mean that i7 would be a long time coming to a general Apple desktop machine. That would be enough to cause me to punt with respect to any new iMac.
Dave