ejolson wrote: ↑
Tue Aug 20, 2019 4:17 pm
If the pinout is different, would a carrier board be possible?
I don't think so. The extra pins are for more channels. It wouldn't be fun to make with the high speed signals present anyway. $10 double sided prototyping PCBs from China aren't going to be good enough.
I don't consider this to be a viable option for reasons you'll see but the closest "active" part is MT53D2048M32D8QD-053WT
which is 8GB x32 LPDDR4 in what appears to be a 200 pin BGA package but slightly thicker due to the additional dies. I say "active" because it has a 6+ month lead time so there are doubts about it actually being in production. The other major issue is that they cost £139 each and you need to buy a tray of 2000.
£173 for an 8GB Pi 4 isn't worth it especially since you still need to patch the closed source bootloader and there is no public datasheet to confirm the specifications of the RAM or how to configure the memory controller. If an 8GB Pi 4 appears then it'll be from Raspberry Pi themselves. Unlikely however due to the price of the RAM. Good luck to anybody crazy enough to want to DIY one. Maybe you can get a sample from Micron.