No, that his the "base die" - a N6 based die that will have I/O, memory controller, SRAM. There are 4 of them, and each one is 300-350mm2.
Here is a picture from MLID that makes it clearer:
View attachment 76039
The silicon interposer is underneath all of these stacked dies, these being:
- 8x stacks of HBM
- 4x of base die with compute stacked on top of these.
As far as the connections in the picture above, each of the 4 pair of HBM memory most likely only needs to talk to their adjacent base die.
So, one way to save on the size of the silicon interposer would be to have 4 or those connections using different technology.
But the 4 base dies need to have a high bandwidth, low latency interconnect, so possibly the silicon interposer would only be under those 4 base dies.
Intel is using EMIB in SPR to connect the "tiles", but I think the bandwidth requirements of the disaggregated GPGPU is an order of magnitude (or more) higher bandwidth than what SPR requires.
BTW, this may mean nothing, just a rumor, but there is a rumor out there that AMD had yield issues with EFB of the Mi250.