How many threads can they add to these dual core processors? Why not just do that instead in adding physical cores.
Going past two threads per core would make no sense. Remember, threads don't process themselves, it's the actual physical processor core that does the processing of threads. Think of HyperThreading as of way to optimize resources that physical cores have.
If you've noticed, Intel's dual core Core i3 processors can work four threads, but they don't double up on performance and they sure can't match true quad core performance. It's just that Hyper Threading makes sure all the resources (or horsepower if you will) one core has are utilized.
Plus I heard with Sandy bridge Intell will be adding a new socket LGA1155. If this is the case are they going to keep both 1155 and 1156 sockets or will they be compatible?
I tried avoiding this topic in reviews as I feel it would bring nothing but confusion, but now that you've opened Pandoras box we can get this out the open.
Lynnfield based processors (Core i7 800 and i5 750) use LGA 1156 socket.
Clarkdale based processors (Core i5 600 and i3 500) already use LGA 1155 socket, which is what you get when you buy H55/H57 motherboard. For now LGA1156 processor is compatible with LGA1155 motherboard and vice verse, and I believe that it will stay that way for all of the current Intel processors on the market.
As for Sandy Bridge... little details are known so far, but word is that Sandy Bridge processors will require new chipsets to work. So even if you buy an LGA1155 (H55/H57) motherboard now, you may end up short with chipset support when Sandy Bridge comes. This is yet to be confirmed but it makes sense since Sandy Bridge will be very different from today's Clarkdale (ie IMC, IGP, PCI-E bus integrated with CPU cores on one die piece)